One of the exciting activities in Krabi is an island hopping tour. We went this tour from The Tubkaak Krabi Boutique Resort hotel. You can charter a small boat called long-tail boat with about USD 50 for 2 people and for 5 hours, but the price and the trip time depend on which course you will take.
I recommend you will start going to the tour early time. Many tourist take this kind of tour, so you will see many people at every islands you visit. But you will be able to enjoy beautiful islands sight seen with less people if you go early time.
You will enjoy beautiful beach with clear water, impressive landscape and many colorful tropical fishes.