Swimming with our mammal friends, in pens

To swim with caged animals is worse than kissing your sister. Look at the critters, will you? They do what they do for a food reward. How many survive a year in the capitivity that they call home? We saw a nurse shark in a pen that was maybe 15 feet wide, 10 feet across, and 4 feet deep, with 3 trimarans of 30-50 people each, lined up to have their pictures taken with the shark. 4 of us went out that day to snorkel and drink, and visit Isla Mujeres, stayed on the boat, did not need to hold the shark. The poor dolphins get captured, get penned up, and are expected to perform for food and not bite anyone. How many die of stress related problems, does anyone think about that?