First, I want to congratulate you on keeping your cool with some of the posts... Not only is taking it slow the right thing to do for safety reasons, but clearly a bunch of them missed the part about it being on public property and the authorities giving you the ok to check things out so long as you returned things to their original state (IE not chisel and sledge to the cap...). Ignore the rest of them, stay the course, and keep us posted.
I'm going to guess that was a group of LARPers (Live Action Role Play). That is where a group of people dress up in period clothing and fight with foam or wooden swords...
In addition to the weight on a string suggestion, I would see if you can find your self an ice fisherman... I have an underwater camera that I use while ice fishing that has a battery powered monitor, and a water proof camera on the end of a 100' cable. Mine also has a built in Infra-Red LED light system, and a detacable white light LED flashlight.