Which of the following is not part of a shark's anatomy?

Poor things have to keep swimming in order to breathe I believe.

I was wrong. There are sixgill and sevengill varieties that have a single dorsal fin. Most sharks have five gill slits on a side.

Player Elf Counsel, there are many species of shark that sleep on the seabed, often under coral or rock ledges

Player Elf Counsel, That is indeed true

As long as they have to swim to breath, I guess a swim bladder isn't necessary. Some sharks have a comparatively very small 2nd dorsal fin, but it is there.