Amphibious. Fhenimore can breathe air and water.
Blood Frenzy. Fhenimore has advantage on melee attack rolls against any creature that doesn't have all its hit points.
Innate Spellcasting. Fhenimore's spellcasting ability is Wisdom (spell save DC 13, +5 to hit with spell attacks). It can innately cast the following spells, requiring no material components:
At will: command, create or destroy water
1/day each: call lightning, Evard's black tentacles
3/day each: control water, darkness, water breathing, water walk
Thunderous Touch. Melee Spell Attack: +5 to hit, reach 5 ft., one creature. Hit:27 (5d10) thunder damage.
Multiattack. Fhenimore can attack once with her bite attack and once with Thunderous Touch.
Bite. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit:8 (1d10 + 3) piercing damage.