I've always liked this story...

http://www.niagarafrontier.com/fallsstopped.html

"A number of people made their way into the gorge to the riverbed. Here they saw articles that had been laying on the river's bottom and had been hidden for hundreds of years. Souvenirs picked up included bayonets, guns barrels, muskets, tomahawks and other artifacts of the War of 1812."

(Even though 36 years isn't hundreds of years.)