I have visited Thailand on 9+ occasions and first used John William's Siam Dive and Sail in 1997 - they are top rate outfit and John knows the area like the back of his hand. He is a graduate of Brooks Photographic Institute in Santa Barbara, CA and co-authored the recent Lonely Planet book on diving around Thailand. The
Siam Dive and Sail website is a wealth of information in itself. I would highly suggest contacting John, tell him exactly what you want/your budget and he can put it all together for you from airport pick up, hotels, and diving.
If at all possible, INSIST on diving at Richielieu Rock near the Similan and Surin Islands. It is a pinnacle that rises from the depths and has a LOT of variety in sealife large and small. Here is a link to my underwater photos on Nikon's website that I took from my trip last Dec to Thailand and Burma. Although the majority of the week long liveaboard was in Burma, about 20% of the photos were taken at Richielieu. It is rather slow loading the 23 underwater photos, my apologies:
CLICK HERE for underwater photos from last years dive trip to Richielieu Rock Thailand and Burma, select ENTER to see the 23 photos or play the SLIDESHOW option
The Similan Season starts in October and you will see many of the colorful soft/hard corals that you wished for plus clownfish, anenomes, and cuttlefish. It is a bit too early in the season to sea Mantas or Whale sharks, but it is always a possibility.
Currents are not usually a problem, but Thai people are very service oriented, just let them know your limits.
Most Phuket operators will offer you day trips to the local spots for about $50 (2000 Baht); Shark point, anenome reef, Koh doc mai, King cruiser, Koh Rachaa Yai, Noi, etc and although these are convenient and very nice they do not compare with the Similans or Richielieu Rock. If you can afford the best then insist John book you on the Ocean Rover Live aboard to Burma (it also dives Richilieu Rock) . I was on a budget so chose the Sai Mai (silk thread) live aboard boat to Burma as it went to the same areas at 25% lower price but had far fewer facilities.
Should a live aboard not fit your plans, I have heard that were some high speed boats that could make Phuket to Richielieu Rock and back in a day and these would be a very attractive alternative for a land based trip as it would allow you to concentrate on the great diving at Richielieu Rock.
The main Tourist town on Phuket Island is Patong and there is a seedy element there, but in defense of Thai people these are mostly frequented by foreigners.
In any case, these "bars" are restricted to 2 blocks on Soi Bangla (Sea Dragon Street) and the rest of the town and beach area is not like this at all. The previous gentleman posted a favorable suggestion of Karon Beach, and he is quite right - it is a very nice place to go just 1 mile from Patong town and has a 2 mile long sandy beach. The USA dollar goes a very L O N G way in Thailand and at the end of Karon Beach is a short hill then another beach, Kata Beach. Here you will find nice beachside resorts at a bit more, but still at about Holiday Inn USA prices.
Ask John as he has chosen to live in the Kata area.
If you have the time, take a daylong bus/boat tour to Phang Nga with the exotic limestone landscapes that sharply rise from the sea. The Island's name "Phuket" is a colloquialized version of the Thai words "Phu jet" or "seven mountains" explaining that these exotic landscapes were once mountains, but now eroded by the sea. If you have seen the movie "The Beach" (great photography/poor storyline) then you'll know how exotic the terrain is.
Should you have even more time take a Sea kayak tour around the Phang Nga area, it is very nice. Even though this is a jungle area, I have never had a problem with insects in Thailand. I have also never had a problem with digestive incidents, but I do drink bottled water.
November is a great time to go as the rainey season is over, the weather is nearly the coolest and many exotic fruits are plentiful. It is also just before the high season of December and you can still find bargains on tourist activities or negotiate more successfully.
While there are many cash machines to use your ATM cards, the exchange rate for $50/$100 bills is superior than for $1/$5 USD, and I negotiate aggressively (but politely) when buying items from vendors or scheduling day dive trips. Flash a $100 bill and the standard dive prices melt away. Negotiating is expected in Thailand everywhere except major shopping mall stores.
For the ladies who like to shop (just guessing you may be one), there is an abundance of tailors and high quality fabrics, but styles are 5 years behind NY. One of my friends brings her favorite blouse, etc as a pattern and has several of the same custom tailored silk in various colors at a fraction of Macy's/Saks prices.
I have never experienced thievery in 9+ visits to Thailand and found the people to be very service oriented and happy spirited.
Sanook mak (enjoy) Amazing Thailand!