ne large amphibious fey 

Perception +16; low-light vision

Languages Aklo, Common, Sylvan

Skills Athletics +19, Intimidation +19, Nature +16, Stealth +18, Survival +16

Str +6 Dex +3 Con +4 Int +1 Wis +3 Cha +4

Items +1 striking bastard sword

AC  28; Fort +19, Ref +16, Will +20

HP 190; Immunities poison, disease; Weaknesses cold iron 10

Frightful Presence (aura, emotion, fear, mental) 30 feet, DC 25

Purity Vulnerability Unpolluted fresh water burns a nuckelavee like acid, dealing 1d6 damage to it and causing it to be sickened 2. A nuckelavee can't heal from damage when it's in an area that isn't polluted (subject to GM discretion).

Attack of Opportunity [R]

Speed 40 feet, swim 40 feet

Melee [>] bastard sword +21 (magical, reach 10 feet, two-hand d12), Damage 2d8+12 slashing plus 1d6 poison and mortasheen

Melee [>] jaws +20 (agile), Damage 2d8+12 piercing plus 1d6 poison and mortasheen

Melee [>] hoof +20, Damage 2d6+12 bludgeoning plus mortasheen

Primal Innate Spells DC 28; 5th control water; 3rd stinking cloud

Breath Weapon [>>] (disease, necromancy, poison, primal) The nuckelavee breathes a 30-foot cone of foulness, dealing 8d6 negative damage (DC 28 basic Fortitude save) to living creatures in the area. A creature that fails also takes 2d6 persistent bleed damage. The nuckelavee can't use Breath Weapon again for 1d4 rounds.

Mortasheen (disease) The target can't recover from the fatigued condition caused by mortasheen until the disease is cured. Mortasheen gains the virulent trait against animals and plants Saving Throw DC 28 Fortitude; Stage 1 Carrier with no ill effect (1 day); Stage 2 drained 1 and fatigued (1 day); Stage 3 drained 2 and fatigued (1 day)

Trample [>>>] Medium or smaller, hoof, DC 28

Bestiary 2, page 186.