When a lake is dewatered the bottom is usually scraped by bulldozers and the material is usually dumped miles away. Just seems to me that the alarm about taking nails and bottles is just a little overkill. Are you telling me no one has officially dug up around Mormon Island? Why arn't they out there now?
It would be fun to find a couple old coins or something. I hear what you are saying but seems like overkill to me. If my grandson and I went out there with a metal detector and found an old coin - it still doesn't make sense to me that I would have to leave it in the mud.
It's state park property and thems the rules. It is basicaly to keep people that go to parks from picking them clean. Like seashells and rocks at the beach. If they didn't have rules, I could see where someone would begin taking down the stone walls to build a cool looking stonewall in their front yard. If everyone that went to the park took one item home with them, the parks would be picked clean of their natural beauty.
When I was out there this past weekend, I was having to tell my 5 year old son to just look and to not pick up things and move them (or throw them in the lake).