It would be nice to see a photo of what you have , it sounds like the moat is too small if ants can avoid the water and go onto the rim . There are other moats or you can make one yourself.

i made a moat from a spray can lid tied a knot in the nylon string threaded thru hole in botttom of lid slid the cap down to the knot and sealed around the string with hard as nails a few ants swam to the lip of the lid. So used a lid off a large peanut butter jar and the string thru the center of lid. again sealing it with nail polish.
it stops most of the ants except an occasional big ant swims to the rim.

Sorry guys, I just found out why the Ant Moat wasn't working. I had the rim of the ant moat touching the top of the roof that's why the ants were getting onto the rim. I just fixed it though.

Great! Glad you found the problem. They really do work amazingly well.

I'm having tthe same problem. The ants are skating across the water, crawl up the inside, walk over the edge to the outside and down the hook. I'm disappointed. Am I supposed to add anything to the water?

Moats never worked very well for me, partly because the wind here blows them around so much I can't keep water in them and the evaporation rate is pretty high (Texas). I put just a little wheel bearing grease on the hookup at a high point where the boss birds are not likely to perch. Ants hate petroleum products. It works well.