On the island of Savai'i we stopped at Satoalepai to swim with sea turtles at a turtle sanctuary who rear and release these amazing (and ancient) creatures.
When we got there, the turtles gathered at the small wharf, and were very keen to interact. They checked us out, but were so gentle in the water. They swam around us without touching, but once we started touching, they would gently put a flipper on you, and when I put my goggles underwater, they eyeballed me through them. One let me rub his nose, clearly enjoying it.
I had read about this experience before we got there, but even I was surprised at how amazing it was. No supervision, no explanation - just pay your 5 Samoan Tala (AUD$2.50) per person, and the turtles are over there. It kind of made it even more exciting - I was hoping they were vegetarian. They have sharp teeth - you should have seen them decimate sugar cane, and 'karate chop' it with their flippers!