uncommon n huge animal aquatic 

Perception +16; darkvision, scent (imprecise) 30 feet

Skills Acrobatics +14, Athletics +20

Str +6 Dex +4 Con +7 Int -4 Wis +4 Cha +1

AC  27; Fort +18, Ref +16, Will +14

HP 170

Buck [R] DC 28

Speed 10 feet, swim 80 feet

Melee [>] tail +18 (reach 15 feet), Damage 2d6+10 bludgeoning

Sudden Retreat [>>] The hippocampus makes a tail Strike, then Swims with a +10-foot circumstance bonus to its swim Speed. It gains a +2 circumstance bonus to AC against reactions triggered by this movement.

Bestiary 2, page 142.