The Thirteenth Year

The Thirteenth Year is a 1999 fantasy comedydrama Disney Channel Original Movie. It was released May 15, 1999. The film was directed by Duwayne Dunham, who has directed other children and Disney movies, including Little Giants and Halloweentown.

After Codys 13th birthday, he begins to feel strange. As he wakes up in the morning, he turns off his alarm clock and zaps it. Ignoring it, Cody drinks from a milk container, which he notices is stuck to his hand he later also drinks large amounts of water. He goes to Jess for help, who agrees to figure Zaleski out whats going on with him as long as Cody teaches him to swim in return. Jess runs various tests, learning Cody can generate electricity, climb walls like SpiderMan, talk to fish, swim extremely fast, and when sometimes wet, scales appear on his hands and arms. Jess concludes that Cody is turning into a merman.Despite all the odd things happening to him, as well as the objection of his adoptive parents when they found out, Cody decides to attend the swim meet. He not only wins the meet and beats Sean, but breaks the state speed record, with his scales appearing. Sean sees the scales and surmises Cody cheated, following him into the locker room. Cody avoids him by sticking to the ceiling, but Sean says he saw something and will find out what. Cody safely makes it out of the stadium and goes home with his parents after they find out he wasnt in his room however, the scales are lasting longer now. ........

Source: Wikipedia