A tiny squib in the Gazzettino suggests that the remains of the Campanile of San Marco has been found in the water about three miles "from San Nicolo'" on the Lido. As you likely know, the original collapsed in 1902 (as oft-seen in the famed but mostly fake photo you see everywhere). Perhaps the rubble was tossed in the Adriatic.
I'll watch to see if there's more on the story. Interesting.