Ramfish (CR 7)

Large Magical Beast (Aquatic)
Alignment: Always neutral
Initiative: +5; Senses: darkvision, low-light vision, Listen +7, and Spot +7

AC: 20 (-1 size, +1 Dex, +10 natural), touch 10, flat-footed 19
Hit Dice: 10d10+43 (98 hp)
Fort +11, Ref +8, Will +5
Speed: Swim 40 ft.
Space: 10 ft./5 ft.
Base Attack +10; Grapple +19
Attack: Gore +14 melee
Full Attack: Gore +14 melee and bite +9 melee
Damage: Gore (2d6+5), Bite 1d8+2
Special Attacks/Actions: -
Abilities: Str 21, Dex 13, Con 18, Int 2, Wis 14, Cha 5
Special Qualities:
Feats: Improved Bull Rush; Improved Initiative; Improved Natural Attack (gore); Powerful Charge; Toughness
Skills: Listen +7, Spot +7, and Swim +16
Advancement: 11-15 HD (Large); 16-21 HD (Huge)
Climate/Terrain: Temperate aquatic
Organization: Solitary, pair, or school (3-6)
Treasure/Possessions: None

Source: Stormwrack

When possible, a ramfish leads off its aggressions by using its Powerful Charge feat to deliver a devastating ramming attack. If it wishes to separate prey from a group, it uses Improved Bull Rush instead. When delivering a bull rush at the end of a charge, the ramfish's total bonus on its Strength check is +11.

Skills: A ramfish has a +8 racial bonus on any Swim check to perform some special action or avoid a hazard. It can always choose to take 10 on a Swim check, even if distracted or endangered. It can use the run action while swimming, provided it swims in a straight line.

Aquatic Subtype

Creatures with the aquatic subtype always have swim speeds and thus can move in water without making Swim checks. An aquatic creature can breathe underwater. It cannot also breathe air unless it has the amphibious special quality.