Can you answer these questions? Sounds like possible RI, but answer the questions so we can better help you

How big is your turtle?
How long have you had it?
What is the water temperature?
Did you use a thermometer?
Are you using a water heater?
How much water is in there?
Are you using a water conditioner?
Are you using any filtration?
What is the basking temperature?
Is there a basking light?
Is there a basking platform that is easy to climb on?
What kind is it or what is it made out of?
Is there a UVB light?
What have you been trying to feed it?
When was the last time your turtle ate?
How big is the tank/pond/enclosure?
Is the tank near a window?
Is the tank in a room with a lot of activity?
Have you read the Basic Care section?
Have you searched the forums for similar situations?
Is there any other unusual activity/symptoms?