Vincent de Phily
Being on a boat doesn't make a restaurant (or anything else) a [tourism=attraction](http://wiki.openstreetmap.org/wiki/Key:tourism).

For permanently-moored boats, it's ok to tag them [building=boat](http://taginfo.openstreetmap.org/tags/building=boat). And as it happens, a lot of objects currently tagged building=boat are restaurants and cafes.