http://www.humanesociety.org/issues/captive_marine/facts/marine_captivit...
Information can be find at this link.
Basically marine mammals have been known to harm their owners and in a few cases kill the trainers.
They often become very ill and their average life span is greatly lessened by living in captivity.
Some dolphins have even been known to bash themselves against the side of tanks in frustration and develop ulcers from stress.
Marine mammals are social animals, in the wild they swim many miles each day in pods. They are also extremely sensitive to sound and living in such small spaces is damaging and disorientating for them.
Please help.