The aircraft does not know and does not care being over whatsoever. "Visual" over water is just a bit boring - looking down at water water water ship water water water ... No problems flying over the channel and the former restrictions, mainly uncomfortable altitudes for crossing, have been eliminated anyways. Do the first crossing together with a fellow pilot having done that before, so you get an introduction on radio communication procedures needed (principles with position reports, border crossing, mid-channel reports are quite similar to ocean crossing, so a nice further education).