Cast Away.

Ron had been a crew member on one of the race around the world sailboats until he was swept over board.  They were ahead of a few boats when they got into a typhoon close to the Philippine islands.
His captain and crew tried to rescue him but when they started to approach a reef, they had to let him go. He was in his life vest and had the radio GPS on. He pulled it out of it's pocket to activate it, when he was hit by a wave and away it went.
He ended up on an island.  He found the island to have a plentiful supply of food, and he was able to stay alive. He began to loose weight and thought this was because he wasn't able to eat enough to maintain his weight. He soon noticed he was getting shorter as well and his hair was growing faster than it usually did.  Not long after that he realized he was too small for they clothing he had. He also found that he was growing breasts and his cock seemed to have disappeared.
He found a shelter after a couple of weeks. By then his crew members would never have recognized him, but they would have certainly noticed him.
He started to wear the clothing that he found in the shelter, though they were just bikinis. He wondered why they seemed to fit him so well.
One day while sitting in the shelter, he noticed a large flat stone that was overgrown with brush that had some odd writing on it. He spent a day clearing the brush off. Though he couldn't read the writing he had the odd feeling that he knew what it said. "You are on an enchanted Island"
"Find the Brasileirinha and you will be able to escape the magic of the island and be transformed to your previous image. Leave without the Brasileirinha and you will continue in your transformed image."
He searched for weeks walking the coast of the island and finally he found it.
As he walked out to it he thought " Am I going to be strong enough to put a hole in this thing and sink it? There is no way that I'm going to change back to a guy just to get off this island."