Echolocation.

The whale can't use its blindsight while deafened.

Hold Breath.

The whale can hold its breath for 90 minutes.

Keen Hearing.

The whale has advantage on Wisdom (Perception) checks that rely on hearing.

Actions

Multiattack.

The whale makes two attacks: one with its bite and one with its tail.

Bite.

Melee Weapon Attack: +11 to hit, reach 5 ft., one target. Hit: 21 (3d8 + 8) piercing damage. If the target is a Large or smaller creature, it must succeed on a DC 14 Dexterity saving throw or be swallowed by the whale. A swallowed creature has total cover against attacks and other effects outside the whale, and it takes 3 (1d6) acid damage at the start of each of the whale's turns. If the whale takes 30 damage or more on a single turn from a creature inside it, the whale must succeed on a DC 16 Constitution saving throw at the end of that turn or regurgitate all swallowed creatures, which fall prone in a space within 10 feet of the whale. If the whale dies, a swallowed creature can escape from the corpse by using 20 feet of movement, exiting prone.

Tail.

Melee Weapon Attack: +11 to hit, reach 15 ft., one target. Hit: 18 (3d6 + 8) bludgeoning damage, or 37 (6d6 + 16) bludgeoning damage if the target is an object.

Sperm Whale