Thap Lamu Pier, in the Thai Muang district of Phang Nga province, is the nearest launching point to the Similans, with boat trips taking about 3 hours.
More adventurous travellers may try to hitch a ride with some of the local boats heading out there - just be sure to allow lots of time since there's no guarantee that there will be a ride back on any given day. Note that a park entry fee of 200 baht is charged.
Daytrips from Phuket and Khao Lak are also possible, with travel time of 45 minutes to 3 hours depending on the boat used. A popular way to go, especially for divers and game fishers, is by joining a liveaboard boat trip from Phuket, which usually run for 4 days. There are many Phuket-based liveaboard operations offering varying levels of luxury and facilities.