What is a Water proof Rivet?

On the right you will see two rivet heads. The one on the left is a good general purpose rivet. The one on the right is called a waterproof rivet.
When the rivet on the left is used, it leaves a gap where the head was pulled through, to set the rivet. The one on the right has a pre-sealed end so that when the rivet is set, it doesn't need to be sealed for water tightness. These rivets can be used on the bottom of fish boats for "small" repairs.
When there is major structural problems you are making a repair for, Pop-type rivets should not be used.