This is on the WSPA web site about what happens to dolphins in captivity
What is the required amount of space for a captive dolphin to be happy? How big are the tanks that they live in when they are not doing shows?
The answer to this question is simple - any tank or enclosure is too small for a dolphin. According to U.S. regulations, dolphin pens only need to be 30 x 30 feet and only six feet deep. With the current U.S. standards, a dolphin would have to circle more than 1.700 times its pen to simulate its natural swimming everyday range in the wild! In warm weather such shallow water Heats quickly. This can be extremely uncomfortable, and often deadly, for dolphins unable to escape to deeper, cooler waters. Not only is there no relief from the heat, but also the dolphin's sensitive skin can be exposed to the sun's Scorching rays, causing blisters and sores. Also, in cement pools, chlorine is added to keep bacteria levels safe for humans. The levels of chlorine used, wreak havoc on a dolphin's skin and eyes, sometimes even rendering them completely blind.
Just because standards exist, does not mean that they're appropriate, well enforced, or they ensure an acceptable quality of life for the dolphins. No facility can not adequately simulate the vast ocean or provide for a dolphin's needs. No captive program - no matter how large, well regulated, well funded, or well intentioned - can make a case for meeting a dolphin's complex behavioral needs and no standard set by a government can be called sufficient.
and this is their website with more info
http://www.wspa-usa.org/pages/2220_dolphins_in_captivity_faqs.cfm#space