Ah I heard all about this yesterday afternoon on the radio.
http://www.bbc.co.uk/iplayer/episode/b02x98fk/Material_World_20_06_2013/
they spoke to the chap doing the research. It was slightly odd because I'd just been looking at some snails at work (as you do). But it was nice to be able to dream up the prehistoric snail-eating on boats connection before they got to it on the programme. Cos as he said, snails don't swim or fly :)

Outrageously it's the wrong type of snail on the photo. Should be one of these colourful creatures
http://www.bily.com/pnwsc/web-content/Photos/Land%20Snails/Cepaea%20nemoralis%20%28Linnaeus,%201758%29,%201.jpg