I went to Mallorca during february a few years back. I would say the air temp was in 60-70's at best, i do recall the hotel pool was like diving/swimming in an ice lake - colder than the UK waters i grew up in, so i would guess low 40's - brrr, the sea temp was a bit warmer though, i would guess 50's, but it was a long time ago, i wasnt a diver then and i was used to UK waters - a lot has changed since then, including my memory. I do recall it was nice and quiet though, nowhere near as busy as the summers with all the Brits aboard down there!