It might be that you don't have time or the motivation for the gym or the thought of running on a treadmill for 30 minutes fills you with dread. So why not dive instead? It's fun, you meet people AND you burn calories!
We should all obviously be fit and healthy before we go diving to help reduce any risks of decompression sickness and ensure our fitness is up to the demands that there can be sometimes, such as current or surface swims. However as a general rule scuba diving and freediving really can help you burn calories.
It's all to do with how your body tries to regulate its temperature when underwater and the majority of the calories are burned during this process. Even a small change in water temperature, that you might not even notice on land will be significant enough for your body to work harder and burn calories!
PADI has done quite a bit of research in this area and the average dive in tropical water, the same as in Koh Samui will burn around 300-500 calories per dive. So rather than worry about the gym or pounding the streets jogging, a much easier, carefree way would be to become a Scuba Diver or Freediver or try and incorporate diving into your weekend time if you're already a certified diver! And if you get involved with the local teams to load and unload the boats then you'll get an additional workout with a bit of weight lifting thrown in!