Yes they sleep underwater
Rhinos don't sleep underwater, but hippos do, they rise to the surface and breath at regular intervals without waking.
Terrapins usually sleep underwater.
yes
No seals do not sleep in pods.Seals sleep upside down on there back underwater or above>.
Yes! Alligators can stay underwater for hours at a time and come out at day.
they sleep for about 2 through 2 hours with their eyes open
Armor for Sleep.
They do not sleep underwater but when resting, it lies at the bottom, buried in sand or mud, lifting its head to breathe or snatch at prey.
Electric eels sleep in the water that they are living in. These eels will typically sleep in dark underwater coves.
Lizards can sleep in trees, under rocks or leaves, or underground burrows. Some can even sleep underwater.
To be able to sleep underwater, you would need to have very advanced equipment to help you cope with the conditions. For example a wetsuit, and oxygen tank/mask of some sort, and other things. But if you were to randomly attempt to sleep underwater, you would drown.
No, they are mammals which means that they have lungs, so they can't sleep underwater any more than you or I could.