Dugongs can breath underwater for about 20 minutes when I went to sleep, dugongs down vertical and remain still on the ground, the sea 20 minutes prior to breathe again.
Manatee can hold their breath underwater for about 20 minutes to sleep. Manatee will be dropped vertically. And lying motionless on the sea floor about 20 minutes before coming up to breathe again.
Manatees can breathe underwater for a long time about 20 minutes when to sleep, manatees are dropped into the vertical and lie still. With the sea floor about 20 minutes. Before coming up to breathe again.