I agree with what the others said. Make sure he's got adequate temperature at all times plus healthy food and supplements. It sounds like he might be a bit cold and undernourished. If you let him swim, dry him off thoroughly and put him under the heat lamp. You might want to get a thermometer where you keep him to make sure that it's warm enough. Plus, make sure the lamp is placed where he can get away from the heat if he wants to. Also, make sure any water you place with him is not too deep.