Dear Anne, I live in a village near the Lake, and i know your story.
With my group of scuba divers (Assopaguro Association) we have already found another B-24 on the seabed of Montalto di Castro, Central Italy.
With a help of others friends we have classified the bomber (a B-24 H, serial number 41-28677), and we shot a film (section "video" in our web site
www.Assopaguro.net).
But I believe that the plane wich I'm talking about is just a B-17. Witness have told me this.
When I know something more definite I'll let you know.
Best regards Victor