Several companies operate boat trips from Tauranga where you can swim with dolphins. Sometimes you can also see other sea life including fur seals, blue penguins, whales and turtles on these trips.
Dolphins are wild animals so there is never a 100% success rate of seeing or swimming with dolphins on these trips; however, the chances are high with Dolphin Seafaris claiming a 95% success rate of viewing dolphins and an 85% success rate of swimming with dolphins (you are not allowed to swim with dolphins if there are baby dolphins present in a pod). They also offer a ‘dolphin guarantee’ where you get a second trip for free if you don’t see dolphins first time around, but the guarantee only applies December–March.
These tours take around five hours and trips operate from November to early May.