Koh Tao Thailand like many dive destinations, is not exactly accessible.
Eight to ten hours south of Bangkok by train to Chumphon then a 3 hour ferry hour puts you at the pier on the west side of the island.
Most of the dive shops, restaurants and places to stay are in this area.

I stayed at Ao Tanote for 4 days, another 20 minutes away. My beach front bungalow was clean, comfortable and basic - no AC, no TV, no phone, no Internet.
But the price was right at 500 baht (about $17 US). Food was good, if you like Thai food.

Diving was coordinated by the neighboring Black Tip Dive resort, a PADI operation with friendly staff.
For diving, we had to travel back to the other side of the island to catch the boat.

The diving was OK, but just OK. Plain and tame. The reef was reasonably healthy with a fair number and variety of fish.
But the presence of other boats indicated that you certainly were not on the leading edge of frontier diving.

Koh Tao is known for its numerous dive operations offering inexpensive courses for basic, open water and dive master certification.
With little current or surge to speak of at least when I was there, the water was ideal for the novice or student diver.
Avid divers however would likely be happier at Ranong or Phuket.

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Or you could fly to Koh Samui and then take the boat from there to Koh Tao. Gets you there much quicker =)

/Björn

or head for phuket and go north west to the similan and surin islands for some better than average diving.

or head south of phuket and dive hin daeng and hin muang, i think the diving on that side of thailand is much better.

stew

Well that depends on what you are looking for. Down at Chumporn pinnacles, there are bullsharks and whalesharks frequent the area as well. The Andaman side has sadly lost much of it sharks to finners.