Multiattack

The dragon makes three attacks: one with its bite and two with its claws.

Bite

Melee Weapon Attack: +9 to hit, reach 10 ft., one target. Hit: 16 (2d10 + 5) piercing damage plus 5 (1d10) cold damage.

Claw

Melee Weapon Attack: +9 to hit, reach 5 ft., one target. Hit: 12 (2d6 + 5) slashing damage.

Tidal Breath (Recharge 5-6)

The dragon exhales a crushing wave of frigid seawater in a 30-foot cone. Each creature in that area must make a DC 16 Dexterity saving throw. On a failure, the target takes 27 (5d10) bludgeoning damage and 27 (5d10) cold damage, and is pushed 30 feet away from the dragon and knocked prone. On a successful save the creature takes half as much damage and isn't pushed or knocked prone.