Anchors...

[Timeliner]

I guy that I know always carries a little box of Dental Floss and a few Balloons.

When he finds something cool he inflates a balloon and ties it off to the floss and sends it to the top to act as a marker. Then he attaches the floss at his end to the fantastic find of the day.

 

[Cave Diver]

I've heard rumor that Academy has those critters for cheap in the fishing section.

[hijack] Hey Chris! How's it going? [/hijack]