Mucous Cloud

While underwater, the creature is surrounded by transformative mucus. A target that touches the creature or that hits it with a melee attack while within 5 feet of it must make a Constitution saving throw (DC = 8 + proficiency bonus + Constitution modifier). On a failure, the target is diseased for 1d4 hours. The diseased target can breathe only underwater. (Aboleth, pp.12, MM)