When I lived in Texas I had a fiberglass boat that was almost impossible to get the plug in from the inside, as you had to reach your whole arm length to insert it and then to tighten it. I installed an automatic plug that had a small cage with a plastic ball in it that would seal the drain hole when the boat was in the water. The great thing about it was it would drain any water in the bilge when the boat got up on plane. Similar to the one below:
Auto Drain Pluug
There are others like this one also:
Metal Automatic Drain Plug