Grilling fish

"My husband and I tried to grill fish this weekend. We have a medium sized coleman charcoal grill. The fish didn't contain any skin. It was a disaster. We overcooked the fish and couldn't get the fish off the grill. How does one keep the fish from sticking to the grill when it doesn't have any skin. We have cooked fish before with the skin on and didn't have any problems, but now we can't find fresh fish with the skin on."