I'm new here - your post has prompted me to register!
The Similan Islands are a stunning destination. My husband and I completed our PADI o/w on a 4 day liveaboard in the Similans in January. We went on the Queen Scuba out of Khao Lak which has a new boat (with a huge dive deck), helpful thai crew and experienced staff.
The diving in Similans and Surins was out of this world. Location-wise, we were spoiled rotten for our first trip! We had some sheltered and fairly shallow (10m) bays to do our early dives, progressing to beautiful sites like East of Eden and Ko Bon and ended up at Richelieu Rock where there were some very strong currents. As new divers, although some of it was pretty challenging, it didn't overwhelm us! I think if you go with a good operation you'll be fine. We dived in small groups according to experience, each group had an instructor. The Captain assessed the currents for safety before a dive group jumped in, and adjusted the schedule as needed. Safety was the highest priority (as it should be!) and we had a really good trip. So good we are considering going back next year![/QUOTE]
Glad you had a good trip on Queen Scuba moraygirl. We had a lot of our customers on that boat last season and had 100% positive feedback. Very good staff who made for fun trips. Of course now they've gone and put the price up quite a bit for next season...
Generally speaking, Similan Islands and other sites dived on these liveboards are OK for all divers, IF the boat and crew can look after you. Some of the sites like Elephant Head, Koh Tachai, Boulder City (to name but a few) can have pretty strong currents and are not shallow dives. Be aware that it is not all easy drift diving along a pretty reef, though if you dive at East of Eden, Breakfast Bend or Koh Torinla (Surin), you get that too.
A couple of suggestions for less experienced divers:
If you didn't dive for a while, do a refresher before the liveaboard trip. It will make your trip safer and more enjoyable. Preferably do more than just a few skills in the pool. Go on an easy day trip with 2 dives or at least a beach dive or 2. Actually this goes for all divers. You want to be sure you are ready for the trip and have confidence in your diving ability. if possible try to use the same gear for the refresher and liveaboard, so you also know your equipment and are sure everything works fine.
If you are Open Water certified, you can do the Advanced Open Water course on the boat. I think all boats offer this. The charge is somewhere from 4 - 6,000 Baht depending on the boat. This ensures that you do some extra theory and get proper supervision from an instructor. The liveaboard may well be your first deep dive, night dive and may be the first time you have experienced currents. Use the knowledge of the staff on board to help you. I find that less experienced divers finish a liveaboard trip with vastly improved skills, air consumption and are able to get much more out of their diving from then on. After one liveaboard, you're hooked!
Wishing you all happy diving