For the cheapest trip to 5 islands, consider taking the snorkeling tour run by Perm Poon Sub. In 2010, the same boat was doing a 4 islands tour. The boat has now been upgraded, and has some comfy chairs and cooling fans in an enclosed area. The boat still has sun decks also, so you can easily top up your sun tan.
Key Points: Pick up time: 08:15. Drop off time: 17:30. Lunch provided. National Park Fee: 200THB. Price: 700THB, Kids half price.