Armor Class 20
Hit Points 356 (23d20 + 115)
Speed 20 ft., swim 50 ft.
Saving Throws CON +11, WIS +7
Damage Resistances fire
Senses Darkvision 120 ft., passive Perception 11
Languages Draconic, Primordial (Aquan)
Challenge 17
Amphibious. The dragon can breathe air and water.
Multiattack. The dragon makes three Bite attacks. It can replace one attack with a Tail attack.
Bite. m +13, reach 15 ft. Hit: 23 (3d10 + 7) Piercing damage plus 7 (2d6) Fire damage. Being underwater doesn't grant Resistance to this Fire damage.
Tail. m +13, reach 15 ft. Hit: 18 (2d10 + 7) Bludgeoning damage. If the target is a Huge or smaller creature, it has the Prone condition.
Steam Breath (Recharge 5–6). con DC 19, each creature in a 60-foot Cone. 56 (16d6) Fire damage. Half damage. Being underwater doesn't grant Resistance to this Fire damage.
Monster Manual (2024), p. 103