Bring a life vest if you are not provided with one. Wear a swimsuit as well as a wet suit to wear over it. A wet suit will keep you warm during long stretches of time in the water. Make sure to bring a cover-up as well as dry clothes to change in to after swimming with the dolphins.
Make sure you are not sick; you could transmit diseases to the dolphin or other swimmers.
Remove any jewelry before entering the water. Necklaces, bracelets and rings can pose a threat to both you and the dolphins. Long necklaces can get caught in a dolphin's flipper, and you could unwillingly be dragged by the dolphin. The dolphin could even eat your jewelry and get sick.
Approach a dolphin with caution and respect. Let the dolphin come to you.
Avoid the eyes or the blowhole when petting a dolphin. Both can become irritated and can hurt the dolphin.
Watch the dolphin carefully for warning signs. Though dolphins are social animals, they do have bad days. If the dolphin seems angry and swims away from you, do not follow without an OK from the trainer. Also watch for signs of tail thrashing or jaw snapping. These are clear signs that the dolphin is agitated.