uncommon cg large amphibious dragon water 

Perception +15; darkvision, wavesense (imprecise) 60 feet

Languages Aquan, Common, Draconic

Skills Acrobatics +16, Arcana +14, Athletics +19, Deception +14, Intimidation +16, Nature +15, Society +14, Stealth +16, Survival +13

Str +5 Dex +4 Con +3 Int +2 Wis +3 Cha +2

AC  27; fed by metal; Fort +17, Ref +18, Will +15

HP 140; Immunities paralyzed, sleep

Countered by Earth If the sea dragon is targeted with an earth spell or flesh to stone, they lose Liquefy until the end of their next turn.

Fed by Metal (arcane, transmutation) When a sea dragon is struck by a weapon made primarily of metal or affected by a spell that uses metal, many of the dragon's scales transform to mimic the metal. This grants the dragon a +1 item bonus to AC until the start of their next turn.

Frightful Presence (aura, emotion, fear, mental) 90 feet, DC 24 (page 305)

Liquefy [R] (abjuration, arcane, water) Trigger The dragon is targeted by a Strike or spell that could deal fire or physical damage to them; Effect The dragon liquefies, turning entirely to water while maintaining their shape, for a split second. Against the triggering effect, they gain resistance 15 to fire and to all physical damage.

Speed 30 feet, fly 100 feet, swim 50 feet; water walk

Melee [>] jaws +20 (reach 10 feet), Damage 2d10+11 piercing plus hyponatremia (page 78)

Melee [>] claw +20 (agile), Damage 2d8+11 slashing plus Grab

Melee [>] tail +20 (reach 20 feet), Damage 2d8+11 bludgeoning plus Grab

Arcane Innate Spells DC 26; 2nd endure elements (self only); 1st create water (at will); Constant (2nd) water walk

Breath Weapon [>>] (arcane, evocation, water) The dragon shoots a ball of water that deals 9d6 bludgeoning damage in a 20-foot burst within 40 feet (DC 26 basic Reflex save). All non-magical fire in the radius is extinguished. The dragon can't use Breath Weapon again for 1d4 rounds.

Coiling Frenzy [>>] The dragon makes one claw Strike and one tail Strike in either order, each against the same target. If either Strike hits, the dragon automatically Grabs the target.

Constrict [>] 2d8+6 bludgeoning, DC 26

Draconic Momentum The dragon recharges their Breath Weapon whenever they score a critical hit with a Strike.

Hyponatremia (water) A living creature that takes damage from the sea dragon's jaws Strike must succeed at a DC 26 Fortitude save or become sickened 1 as a surge of excess water floods its body.

Bestiary 3, page 77.