uncommon n gargantuan animal 

Perception +22; darkvision

Skills Acrobatics +18, Athletics +26 (+28 to Swim), Stealth +28

Str +8 Dex +4 Con +6 Int -4 Wis +2 Cha +0

Undetectable (abjuration, primal) A sea serpent automatically tries to counteract any detection, revelation, or scrying divination attempted against it, using its Stealth modifier for its counteract modifier.

AC  35; Fort +25, Ref +21, Will +21

HP 210

Speed 20 feet, swim 60 feet

Melee [>] jaws +27 (reach 20 feet), Damage 3d10+14 piercing plus Grab

Melee [>] tail +27 (agile, reach 30 feet), Damage 2d10+14 bludgeoning plus Grab

Ranged [>] water spout +25 (brutal, range increment 100 feet, water), Damage 2d6+12 bludgeoning plus sea serpent algae

Capsize [>] (attack) The sea serpent attempts to capsize an aquatic vessel of its size or smaller that it's adjacent to. It must succeed at an Athletics check with a DC of 35 or the pilot's Sailing Lore DC, whichever is higher.

Constrict [>] 1d10+14 bludgeoning.

Sea Serpent Algae (incapacitation, poison) Saving Throw DC 34 Fortitude; Maximum Duration 6 rounds; Stage 1 confused and, if flying, spends its first action each turn to descend 20 feet (1 round); Stage 1 confused and, if flying, descends until reaching the ground or water below (1 round)

Spine Rake [>>] (attack, move) The sea serpent extends the spines along its back and Swims or Strides. Each creature the serpent is adjacent to at any point during its movement takes 4d6+8 slashing damage (DC 32 basic Reflex save).

Swallow Whole [>] (attack) Huge, 2d10+6 bludgeoning, Rupture 20.

Bestiary, page 288. Expanded in LOIL.