Marine Terrain & Voyages

Marine Dungeon Terrain

Ship interiors, sea-floor dungeons or ruins, and water-filled chambers in more conventional adventure sites often feature specific types of walls, floors, or other dungeon dressings. In addition to the special materials and features described here, simple hewn or dressed stone walls and floors are every bit as commonplace in watery chambers as they are in dry ones.


Walls inside a ship are more properly called bulkheads. Bulkheads serve the same purpose on board a ship as walls do in a building; they partition the ship into discrete compartments, and they strengthen the overall structure. Other types of walls found in marine dungeons are described below.

Wall TypeTypical ThicknessBreak DCHardnessHit Points
Bulkhead3 inches16530
Coral3 feet457480
Hull, heavy8 inches28580
Hull, light4 inches20550
Hull, reinforced1-1/2 ft.406150

Bulkhead: A typical interior partition inside a wooden ship. Bulkheads are usually smooth, finished wood, with a Climb DC of 25.

Coral: Dead coral can be cut and hewn much like limestone or similar materials. When such a wall partitions two chambers, it is usually at least 3 feet thick in order to support the weight of the coral above. It takes a DC 22 Climb check to climb a wall made of coral.

Hull, Heavy: Ships and boats of Gargantuan size or larger normally have heavy hulls. Heavy hulls consist of sturdy, waterproofed planks backed by more planks, fixed to a reinforced strong skeleton of timbers. Hulls offer few handholds for climbers (Climb DC 25).

Hull, Light: Most ships and boats of Huge size or smaller have light hulls. Light hulls consist of sturdy, waterproofed planks fixed to a strong skeleton or framework of shaped timbers. like heavy hulls, light hulls offer few handholds for climbers (Climb DC 25).

Hull, Reinforced: large warships often have reinforced hulls. Reinforced hulls have a thick backing of solid timbers designed to help the outer hull absorb and resist heavy impacts such as catapult shot. Reinforced hulls are just as hard to climb as other hulls (Climb DC 25).


Floors usually don't matter much in submerged dungeons or water-filled chambers, simply because many characters (and most monsters) are swimming instead of walking. However, there are exceptions - a monstrous crab or a heavily armored character with a water breathing spell might do better walking along the bottom and fighting with feet planted on the sand or muck.

In order to obtain firm footing and effectively walk along the bottom, a character or creature must meet one of two requirements:

Characters or creatures walking along the bottom are subject to the conditions of the floor, just as characters walking on land would be.

Muck: Tidewaters and estuaries, abyssal floors, river bottoms, and lake bottoms are often covered in muck a foot or two deep. Creatures on foot pay 4 squares of movement to enter each square of muck, and running and charging are impossible. The DC of Tumble checks increases by 5.

Pebbles: Weed-covered pebble bottoms are common in colder lakes and ocean waters. They are easier to maneuver in than muck but somewhat more slippery and treacherous than clear sandy bottom. Creatures on foot pay 2 squares of movement to enter each square of sandy bottom, and running and charging are impossible. The DC of Tumble checks increases by 5.

Sand: Underwater sand is wet and well packed, offering good footing. However, plodding along the bottom is tedious work even in good conditions, and creatures on foot pay 2 squares of movement to enter each square of sandy bottom. The DC of Tumble checks increases by 2.


Many marine adventures revolve around a ship's voyage. This can be a routine crossing between heavily trafficked ports, a search along the coast for a hidden pirate lair, the quest for a mythical floating island, or a bold expedition to find and chart new lands across the ocean.

Extended travel over the ocean is an adventure in and of itself, especially in uncharted and dangerous waters. A party of heroes might encounter terrible monsters of the deep, mysterious islands haunted by sinister perils, fearsome storms, shipwreck, or disaster in a dozen different forms.

During each day of a voyage, you should check for four things: weather, navigation, encounters, and the day's progress. If stores or supplies are running short (for example, the heroes are adrift in a small boat with no food or water), you might need to add extra steps to track successful use of the Survival skill, consumption of stores, and similar tasks.

Wind And Weather

Few factors play as prominent a role in determining the success or failure of a voyage as the weather the ship encounters. Fair winds make for a swift, easy crossing, but storms and calms can frustrate even the most skillful of sailors.

Weather: At the outset of the voyage, roll on Random Weather, Wind, and Precipitation to determine the current conditions. Use the column corresponding to the climate the ship is currently in (cold, temperate, or warm). Seasonal variations can move you to a different column - for example, in summertime roll on the temperate column for ships in otherwise cold climates, and on the warm column for ships in otherwise temperate climates.

The result of this roll gives you the temperature, wind strength, and precipitation for the day. Refer to Weather for details of these effects.

Once you roll a set of weather conditions, they persist without changing for 1d6 days.

Random Weather, Wind, and Precipitation
Cold¹Temperate²Warm³TemperatureWind Precip.
- -01-03Severe heatFair Clear
- -04-05Severe heatVaries Clear
-01-0206-14HotFair Clear
-0315-19HotFair Rain
-04-0520-25HotVaries Clear
01-0306-1526-50WarmFair Clear
0416-1951-65WarmFair Rain
05-0720-2966-70WarmVaries Clear
0830-3271-76WarmVaries Rain
0933-3577-80WarmStorm Rain
10-1736-5981-87ModerateFair Clear
18-2160-6388-89ModerateFair Fog
22-2464-7090-91ModerateFair Rain
25-3071-8092-96ModerateVaries Clear
31-3281-8397-98ModerateVaries Rain
33-3484-8599-100ModerateStorm Rain
35-5786-91-ColdFair Clear
58-6292-93-ColdFair Fog
63-6694-ColdFair Snow
67-8295-98-ColdVaries Clear
83-8699-ColdVaries Snow
87-89100-ColdStorm Snow
90-94--Severe coldFair Clear
95-98--Severe coldVaries Clear
99-100--Severe coldStorm Clear
¹ In summer, use the temperate column for cold marine climates.
² In winter, use the cold column for temperate climates; in summer, use the warm column.
³ In winter, use the temperate column for warm marine climates.

Wind Strength: To determine the specific wind strength and direction, use the general wind condition indicated by the result of Random Weather, Wind, and Precipitation and roll on the corresponding column on Random Wind Strength.

Wind strengths correspond to the wind categories on Wind Effects.

Sailing Speed: This is the multiplier used when determining the speed that a sailing ship can make given the current wind conditions. For example, a ship with a sail speed of 20 feet has a speed of 40 feet under a moderate wind.

In the absence of any wind, the ship is becalmed and travels at the speed of the current. A ship that loses its sails becomes a derelict drifting with the currents.

A ship in a severe wind can sail only if the captain or master succeeds on a DC 20 Profession (sailor) check. If the check fails, the ship cannot be controlled and is driven by the wind. A ship in a windstorm or gale requires a DC 30 check to sail successfully.

Driven: A driven ship cannot sail or row but is instead driven directly downwind at a speed in feet per round equal to twice the wind speed in miles per hour. For example, in a hurricane of 90 mph winds, the ship is driven 180 feet downwind every round (or 18 miles per hour the storm persists).

Wind Direction: After determining the wind strength, check for the wind direction by rolling on Wind Direction.

Random Wind Strength
FairVariesStormStrengthSailing Speed
10086-9811-50Severe (heavy)x3¹
-99-10051-90Windstorm (gale)x3²
--100Dire galeDriven
¹Requires DC 20 Profession (sailor) check to sail or row; otherwise, driven.
²Requires DC 30 Profession (sailor) check to sail or row; otherwise, driven.
Wind Direction

Wind direction is the origin of the wind; a north wind is a wind blowing out of the north (and therefore blowing toward the south).

Prevailing: If the wind direction is prevailing, it means that the wind simply blows out of whichever direction it normally does given the location and the time of year. For example, a broad ocean can have seasonal trade winds - strong breezes that blow from a certain direction for months in certain latitudes, making ocean crossings relatively easy.

Sailing into the Wind: A sailing ship cannot sail directly at the wind; a ship sailing within one point of the wind (sailing northeast into a northerly wind, for example) is reduced to half the normal speed the wind strength would otherwise indicate. It's possible to tack against the wind by alternating between northeast and northwest, and therefore slowly making progress to the north.


Strong winds bring heavy seas, drive poorly handled vessels into danger, and can batter or sink even expertly handled ships. High winds expose ships to dangerous seas, depending on the size of the ship and the strength of the wind. Ships can roll violently, take heavy sea wash over the deck, or even risk foundering. Check to see if a ship founders due to heavy seas once per day while the ship is caught in the heavy weather.

Storm Perils
Wind StrengthHuge or SmallerGargantuanColossalDC
StrongRolls or washNoneNone5
Severe (heavy)Rolls and washRolls or washNone10
Windstorm (gale)Rolls and wash¹Rolls and washRolls or wash15
HurricaneCapsize and wash¹Rolls and wash¹Rolls and wash20
Dire GaleCapsize and wash²Capsize and wash¹Rolls and wash¹28
¹ Check for foundering once per hour instead of once per day.
² Check for foundering once per minute.

A foundering check is a Profession (sailor) check by the vessel's captain or master, modified by the ship's seaworthiness modifier. On a failed check, the ship founders.

Rolls or Wash: The ship sustains either heavy rolls or it takes green water over the bow or the stern. The ship takes green water over the bow or stern if its bow is pointed straight into the wind or straight away from the wind; otherwise, it takes heavy rolls.

Rolls and Wash: Regardless of which way the bow is pointed, the ship takes both heavy rolls and green water over the deck.

Capsize and Wash: Regardless of which way the bow is pointed, the ship takes both heavy rolls and green water over the deck. In addition, if the ship's bow is pointed at any direction other than straight into the wind or straight downwind, it must check for capsizing once per round. A capsizing check is a foundering check (DC 20, + 1 per previous capsizing check). Remaining broadside on to heavy seas is extremely dangerous, and very likely to result in capsizing the ship.


Ships in strange waters can become as hopelessly lost as travelers in a featureless desert or deep forest. Keeping track of where you are and how to get to where you're going are difficult challenges for many mariners.

Setting Out: The difficulty of setting an accurate course depends on the quality of information you have about where you're going. See Knowledge (geography) for a list of DCs and modifiers for course setting. The DM makes this check for you, since you don't know for certain if you have planned an accurate course.

If you don't have any particular destination in mind, you don't need to set a course. As long as you keep a record of course changes and distances sailed, you won't have trouble retracing your steps or setting a new course.

Daily Piloting: Each day of your voyage, you make a piloting check to establish your position and make the routine corrections necessary to hold to your intended course. Refer to Knowledge (geography) for DCs and modifiers.

Failing your piloting check once is not a problem; you simply failed to establish your location for the day, but you can go back to your previous day's established position and estimate your current position given the course and speed you think you've followed since. You do not become lost until you fail your piloting check on three consecutive days.

Lost at Sea

A ship's chance to get lost depends on the navigational skills of its master, the weather, and his familiarity with the waters through which it sails. Getting lost at sea works much like getting lost on land (see Getting Lost), with a few exceptions.

First, you check to see if you become lost only once per day during extended voyages. (You might need to check once per hour in confined or confusing waters, such as mazelike river delta). A ship at sea is not lost until you fail your piloting check three days in a row.

As on land, a ship lost at sea moves randomly. In order to recognize that you've become lost, you are entitled to a Knowledge (geography) check once per day (DC 20, -1 per day of random travel) to recognize that you are no longer certain of your direction of travel.

Setting a new course once you've recognized that you have become lost requires a new Knowledge (geography) course-setting check. The DC is determined normally, although you should apply the modifier for guessed at an unknown starting point as appropriate. Generally, a ship has an unknown starting point only if it has been driven by a storm or similarly deprived of any method to gauge its direction and distance of travel.


The seas are home to bloodthirsty pirates, vigilant warships, hungry sea monsters, and marauding bands of aquatic warriors. Sooner or later, a seafarer will encounter something she would rather not meet.

You can check for encounters once per hour of travel (good for short voyages) or once per day of travel (good for longer voyages). The chance per day is simply the cumulative chance of having at least one encounter, based on the hourly encounter chances - use one or the other, but not both.

TerrainPer HourPer Day
Coastal waters4%28%
Open ocean1%8%
Well-traveled waters8%49%

Encounter tables for various sorts of marine terrain appear in the Appendix, starting on page 212. (Stormwrack)

Coastal Waters: Waters within 50 miles of shore count as coastal waters, even if the coast is desolate or unsettled.

Open Ocean: Waters more than 50 miles from the nearest shore are considered open ocean. The ocean is vast and desolate by any standard, and ships can go many days between encounters with other ships or dangerous sea creatures.

Well-Traveled Waters: Within 20 miles of human-settled lands and kingdoms, a steady traffic of merchant vessels and warships plies the waters between busy ports.

The Day's Progress

Assuming that a ship at sea doesn't become lost, doesn't encounter deadly weather, and doesn't meet with some ship-devouring monster, it travels some distance along its course each day.

In 1 hour, a ship travels a distance in nautical miles equal to its speed in feet per round divided by 10. For example, a ship sailing at a speed of 30 feet per round is making 3 knots, and covers 3 nautical miles in an hour.

In one day of travel, assuming the ship stops for the night (the common practice along coastlines), a ship travels a number of nautical miles equal to its speed in feet per round. A ship sailing at 30 feet per round covers 30 nautical miles in a day of sailing.

Captains in open waters, or captains sailing under bright moonlight (or otherwise not concerned with being able to see well in the dark) often sail around the clock. Sailing a full 24 hours doubles the normal distance traveled in a day of sailing, so the ship with a speed of 30 feet per round sails 60 nautical miles over a full day.

Sometimes contrary winds or strong currents can prevent a ship from making progress toward its intended destination or force it to sail in a direction other than its intended course.