Ahh...One of my favorite distance swims in Phuket is to swim around PU Island which is located northwest of Kata Beach Phuket. I have to time this swim according to the tides and conditions; generally I like to do the swim during high tide that way I can get the full benefit of the swim, during low tide you can almost walk across parts of the coral that are located around the beach section.
The entire swim takes about 45 minutes with the use of surface swim fins, I use the underwater recovery stroke during most of the swim, this stroke you are using more of your legs to propel you through the water. I would not recommend doing this swim without surface fins because of the currents and it can get a bit choppy with the swells when you are going around the northern tip of the island.
If you want to rest during this swim , rest on the southern side there is less swell and current activity, just be careful of the coral and rocky areas. The marine life during the swim is very beautiful, sometimes you will see a school of barracudas, I notice this more often on the south east side as I am making my way around, they are very harmless , but curious nothing to worry about.
My son took this video just as I was coming in so it is a bit erratic, one day I will get one of those water proof video cameras that I can take on my swims.