A discussion on another topic reminded me of this old trick. If you have any hollow body hard baits that are taking on water they are real easy to fix.
Place the lure in the freezer for a couple of hours, then take it out and immerse it in a glass of hot water, not too hot. The air inside will expand and force bubbles out where the leak is located. Wipe off the lure and smear a little glue over the hole and your are ready to go. This has worked for me every time