One thing I love about living in Oahu Hawaii is that I don't spend a huge amount of money trying to have fun. Previously I lived in Alberta Canada and Idaho USA. To have fun there I could go paint balling, skiing, snowboarding, golfing eating out etc. The tropical beach provides many ways to have good leasure time to free. I love body boarding amid 5-8ft waves. Snorkling is fun although not considered a sport. But perhaps free diving is considered a sport. Cliff jumping is great. I love the HI life! How to have fun with the least amount of money?
I can suggest you a couple of cheap sports, appropriates to the place where you live in now: first of all I suggest running on the beach (maybe listening to music with your smartphone), you can have a refreshing bath after running. Then you can try the "stand up paddle" (quick Google search if you don't know what is it), it's funny and cheap...you have just to buy a board. In the end I can suggest you...dancing everywhere: on the beach, in your garden...dancing is fantastic and free!