Can you please answer some of these questions?
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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?