I was just on the south coast of Altis Island and I spotted a submarine about 200m out when I decided to take the plunge to retrieve it. The problem is as soon as I entered the water I started to lose oxygen. I tried a few more times with no luck and then I figured I would try to swim on my back and that did work for a while but then for some reason I started to lose oxygen again. I was able to make it back to the coast, thankfully, but no matter what I tried I would have ended up drowning in my slow paddle towards the submarine. Any ideas why I was unable to swim without losing oxygen even though my head was above water? Is it possible I weigh too much and I'm actually sinking? Any responses will be very much appreciated.