What to d'o with a suffering fish?

If they are in a tank, make sure they are fed and the water is clean. To clean the tank, remove the fish and put them straight into another source of water. Remember if your fish is salt or fresh water.

If the fish is in the sea, river or pond, its best to leave it.

If the fish is on land near a water source, replace it in there. If it is nowhere near a water source, I have no idea how it got there. You would have to leave the fish then. Sorry if this answer is vague, because your question was as well.