These animals and plants were photographed in the underwater aquarium of El Gouna/Egypt at the Red Sea.
The salt water is continously supplied by compressed air to keep the oxygen content high enough for respiration of the polyps, corals, snails, tube worms, murrays and algae.
The turtle has to swim to the surface to take the air from outside the water.

A diver in the Red Sea:
1. For breathing compressed air (200 bar) in a tank.
2. Against cooling a 1-cm-Moltopren suit.
3. To leave the water surface a weight belt (8 kg lead).
4. For buyancy and to return to the surface an inflatable safety vest.
5. For motion fins at the feet.
MOST IMPORTANT: PROPER EDUCATION FOR DIVING!
More about underwater breathing and about hazards to health