Sealife centres have been in the public eye for all the wrong reasons for many years now (please watch Blackfish on Netflix, if you haven't yet).
A lot has been done to stop this horrendous industry and people are becoming more aware of the cruelty behind a cute dolphin jumping through a hoop.
Dolphins, whales and other marine mammals do not belong in tanks. These gorgeous animals are used to travelling for miles in the ocean. If they cannot follow their instincts to hunt for live food in a family unit or pod, they will become sick and stressed, not to mention the chlorine in 'performance' pools causing them to lose their sonar and/or go blind.
Please do not spend your money on such activities, they are against nature and only ever built for profit purposes, no matter how much the venue might convince you it's for conservation.
There are a handful of genuine sanctuaries that rescue injured or orphaned/abandoned sea mammals and they will tell you the same: that these beautiful creatures belong in their natural habitat, not in a tiny tank to entertain humans.