n medium amphibious animal 

Perception +2; low-light vision, wavesense (imprecise) 30 feet

Skills Athletics +4, Stealth +4

Str +2 Dex +0 Con +3 Int -5 Wis +0 Cha -3

AC  15; Fort +7, Ref +4, Will +2

HP 9

Attack of Opportunity [R] Stinger only (page 304).

Speed 30 feet, swim 30 feet

Melee [>] pincer +6, Damage 1d6+2 slashing plus Grab

Melee [>] stinger +6, Damage 1d4+2 piercing plus eurypterid venom

Eurypterid Venom (poison) Saving Throw DC 14 Fortitude; Maximum Duration 4 rounds; Stage 1 1d4 poison damage (1 round); Stage 2 1d6 poison damage (1 round); Stage 3 1d6 poison damage and enfeebled 1 (1 round)

Bestiary 3, page 97.