Dolphins are a big thing in terms of Mediterranean myth, they have been depicted for many thousands of years. The Greeks liked them and so consequently did the Romans. Dolphins have probably been a traditional form in glass making in Venice probably for most of its existence. Anyway, that would in general terms make me think dolphin before I thought whale. Come to think of it, the head down tail up pose is not unusual either - almost all Salviati's seem to be this way up.
John