Blood Frenzy.

The high priestess has advantage on melee attack rolls against any creature that doesn't have all its hit points.

Limited Amphibiousness.

The high priestess can breathe air and water, but she needs to be submerged at least once every 4 hours to avoid suffocating.

Shark Telepathy.

The high priestess can magically command any shark within 120 feet of her, using a limited telepathy.

Spellcasting.

The high priestess is a 7th-level spellcaster. Her spellcasting ability is Wisdom (spell save DC 14, +6 to hit with spell attacks). She has the following cleric spells prepared:

Cantrips (at will): guidance, mending, resistance, thaumaturgy
1st level (4 slots): bless, detect magic, guiding bolt
2nd level (3 slots): hold person, spiritual weapon (trident)
3rd level (3 slots): bestow curse, fear, mass healing word, tongues
4th level (1 slot): banishment

Actions

Multiattack.

The high priestess makes two attacks with her toothsome staff, or one attack with her bite and one with her claws.

Toothsome Staff.

Melee Weapon Attack: +5 to hit, reach 5 ft., one target. Hit: 11 (2d8 + 2) piercing damage.

Bite.

Melee Weapon Attack: +5 to hit, reach 5 ft., one target. Hit: 4 (1d4 + 2) piercing damage.

Claws.

Melee Weapon Attack: +5 to hit, reach 5 ft., one target. Hit: 4 (1d4 + 2) slashing damage.

Sahuagin High Priestess