Before going to Seaworld, I already planned to watch "The Cove" ( http://www.thecovemovie.com/home.htm ).
I won't talk too much about the issues they address : the best you can ever do is at least watch it. Warning: it may get you Angry against Human being (and against the Japanese Government)
Despite the fact that Seaworld and other great them parks with Cetaceans are indirectly taking part of this shame, I keep thinking that paying a visit to Seaworld is a great idea : these places are well maintained; do respect nature and let you discover the ocean wild life with great educational agenda. I just hope that, in the future, these big companies will be more proactive on preventing Dolphin Slaughter, rather than closing their eyes as they do; rather than even trying to hide this issue (see in the Movie...).