Underwater game

What kinds of things do people usually do in the ocean?

Some people like to swim, other people like to look at fish and some people just like to play.

Well, the people in this picture are playing. They just aren't playing a game people normally play underwater. They're playing cards.

They are over nine meters deep. They are wearing tanks on their back that hold air for them to breathe. The gray squares on top of the table are weights. If the weights weren't there, the table would float to the top of the ocean.

Now that we know how these people are able to play cards underwater, there's only one other question -- ?why would they want to?