Kaikoura, New Zealand
Holy s***... The dolphins in kaikoura are insane. See, I went out swimming with the dusky dolphins today.
What they do is they hook you up with a wetsuit, breif you a bit on what to avoid and what to do and then you go out on a boat to where they've spotted the dolphins.
The unique here is how friendly they are and how often they are found. Keep in mind, they are fully wild so the only reason you get to swim with them is because they like to scare and play with...