I thought Bali was already amazing enough but oh god, after Krabi, Bali seriously pales in comparison. The beaches in Krabi are just wonderful. The water is so clear and calm so it's perfect for swimming. When the tide is low, you can see those little cutie crabs and hermits all over the beach! I remember having to keep aplogizing as I waddle across lagoons at Nopparat Thara beach. Oh, we avoided Ao Nang beach at all cost because it was terribly crowded so thank god our resort's smack right in the middle of Ao Nang and Nopparat Thara. We could actually swim out a little (about 100m) to a random little island across the beach. It was low tide so we just waddled across with our stuffs. You can get waterproof ocean packs along the streets for about $10 so yes, we are well-covered.
Island-hopping tour was beyond amazing. We went to Tup Island, Mawr Island, Chicken Island and Poda Island. You don't really get to Chicken Island. I think it's not accessible to man – I don't remember seeing a beach there. So what happens is that the tour guide will just ask you to jump into the clear green water next to the island and snorkel. With or without life vest, that's really up to you. I only lasted for about 10 minutes without life vest because all the tread-waterings killed my legs. There's plenty of life in that water I swear to god. The coral reefs are so colourful and the fishes weren't the least bit shy. I was weirded out at first when they kept swimming around me but it got OK after a while. Bali suck so bad now – I don't remember seeing that many life underwater.
Anyway, whatever tour prices you see along the streets are bargainable. I recommend Krabi Trek. They listed 4-island hopping at 1,000Thb but guess who paid only 500Thb? Yes, me.