Amphibious. The dragon can breathe air and water.

Petrifying Gaze. If a creature starts its turn within 30 feet of the dracolisk and the two of them can see each other, the dracolisk can force the creature to make a DC 12 Constitution saving throw if the dracolisk isn't incapacitated. On a failed save, the creature magically begins to turn to stone and is restrained. It must repeat the saving throw at the end of its next turn. On a successful save, the effect ends. On a failure, the creature is petrified until freed by the greater restoration or other magic.
A creature that isn't surprised can avert its eyes to avoid the saving throw at the start of its turn. If it does so, it can't see the dracolisk until the start of its next turn, when it can avert its eyes again. If it looks at the dracolisk in the meantime, it must immediately make the save. 
If the dracolisk sees its reflection within 30 feet of it in bright light, it mistakes itself for a rival and targets itself with its gaze.

Bite. Melee Weapon Attack: +5 to hit, reach 5 ft., one target. Hit: 9 (1d12 + 3) piercing damage plus 3 (1d6) poison damage.

Acid Breath (Recharge 5–6). The dragon exhales acid in a 15­-foot line that is 5 feet wide. Each creature in that line must make a DC 12 Dexterity saving throw, taking 27 (6d8) acid damage on a failed save, or half as much damage on a successful one.