Thailand forum

With regards to Koh Tao, I've been a few times (and I'll be back in a few weeks!) and I've found Big Blue Diving has the best combination of staff (many, experienced, and very helpful), location (on the beach at the northern end of Sairee), equipment (clean, plentiful, good quality), facilities (bar, restaurant, small equipment shop, free lockers, etc), and options (novice to professional, tech courses, plenty of day trips and fun dives, three dive boats). It's a large operation so there are open water courses beginning every day (they like to keep group sizes fairly small).

They can also do accommodation and diving packages, although I prefer to arrange my accommodation independently.

There are plenty of other options, though. Ban's and Simple Life get a lot of good things said about them. Sairee isn't the only option, either. It's the busiest and most developed part of the island but there are lots of cool bays with their own small villages and accommodation and diving options.

I was last in Nha Trang a few years back but from my past experience, you don't need to book long anywhere. There are heaps of spots and you need to look at them. Don't get too locked in for a long time cuz you may want to change and it is easy to do. Great place as last poster said.