Pad eyes ?
Pad eyes go on with rivets if you have no inside access. If you have inside access you can use small stainless screws and a backing plate with washers and nuts with nylonloc. That way they will not back out. You can get the pad eyes fairly cheap and I believe the drill hole is 3/16. If you are worried about water seepage put a dab of some kind of water tight sealant that will adhere to the plastic on the yak. good luck video's should be available on youtube