I saw those pics on another website and it was supposed to have taken place in the Chesapeake Bay, near Annapolis

and it's not uncommon to sea deer swimming....many years ago up at Liberty Reservoir my brother and I observed a buck swimming from the Carrol county shore and headding to the Baltimore County side, we tried to catch-up to him but he out swam my brothers 36volt 18' electric jon-boat, which topped out at 7knts....so that deer was haulin' tail
