Just about any of the European cruises! I'm not so sure about Celebrity offering a topless deck. Haven't sailed all their ships, but don't remember any of the ones I have sailed having a topless deck. (I'm sure I'd remember)
Haven't sailed Costa, but I'd guess they'd be the most likely to offer this option, as they're far more "Continental" in most every way. Call or e-mail them as ask.
Ken
"Sky"