I swam in Mediterranean in Italy quite often. There often were white (not spectacular looking) jellyfish around - and quite a lot of them. I tried not to touch them because I was afraid to get burned (even though I don't think that this species stings) and that I'll harm these animals.
However, I am a little surprised that I've managed to never get in contact with one. You can't see them quite good and there a really a lot of them sometimes. Do they actively try to avoid contact?