This Turtle Just Likes to Play Dead

Reminds me of an aquatic frog I had in an aquarium in my biology lab classroom. It would sink to the bottom and rest. My students would think it had drowned and was dead. It was able to breathe through its skin. Sadly one time it accidentally jumped out of a gap in the glass lid onto the lab table counter one night and I found it the next morning really dead.

"Turtles with serious respiratory infections, often those resulting from vitamin A deficiencies, might tilt to the side when swimming, which could cause them to flip over. A lack of vitamin A changes a turtle's mucous membranes in his eyes, mouth and respiratory tract. Early signs of an infection include lack of appetite, nasal discharge, eyelid swelling and discharge, ear swelling and bubbling in the mouth. By the time the turtle starts tilting or flipping, the infection has gone into his lungs. He can no longer stay buoyant in the water. Take your pet to the vet as soon as he exhibits abnormal symptoms or behavior."
https://animals.mom.me/mean-turtle-keeps-flipping-over-11385.html