Huge Beast
Armor Class 12
Hit Points 75 (10d12+10)
Speed swim +60, walk +0
Challenge 3
Senses blindsight 120 ft., passive Perception 12
Echolocation. The whale can't use blindsight while deafened.
Hold Breath. The whale can hold its breath for 30 minutes.
Keen Hearing. The whale has advantage on Perception checks that rely on hearing.
Bite. Melee Weapon Attack: +6 to hit, reach 5 ft., one target. Hit: 14 (3d6+4) piercing damage. If the target is a creature it is grappled (escape DC 14). Until this grapple ends the whale can't bite another target and it has advantage on bite attacks against the creature it is grappling.
Source: Level Up Advanced 5e Monstrous Menagerie · OGL/Open