I'd advise avoiding the trip to the blue cave, we did it, or tried a couple of years ago, with one of the operators near
stay, there was no safety briefing or sign of life jackets on the large rib, when we got to the cave the swell was 2-3ft, not huge but the opening to the cave is quite small so it was either big or no existent depending on timing of the swell. In our group there was an experienced guy with his own mask and fins, he went in first and came back very quickly shaking his head and indicated it wasn't safe, at same time a family of dad and 3 sons had jumped in, the dad struggled with the swell and came back to the boat having taken in a few lung fills of water, the skipper of the boat was oblivious to his problems and he had to be dragged back into the boat by other paying guests, to cap this off his three sons did get into the cave, two came out after a short while and swam back to the boat, at this point his mum frantically shouted where's xxxx, the two other boys said they thought he was still in there, thankfully the experienced guy was still in the water and went back in to see if he was there, after a couple of very tense minutes he came out dragging xxxx on his back in the same was a lifeguard would do, we managed to get both back on board, xxxx was very badly shaken and had lots of cuts and grazes on his body. We had to insist the skipper took,us back to port and rang in for an ambulance as xxxx was coughing up a lot of water,, and the experienced guy discreetly out of earshot of his family said that he had found him face down in the cave and feared the worst.
Back on shore xxxx was checked out by the ambulance that was waiting for us, and thankfully was ok other than the scrapes and being shaken up. I have to point out that at no point did the skipper show any concern.
I am an experienced windsurfer and sailor, with cross channel experience, if I had known how potential dangerous the trip could have been, I wouldn't have subjected myself and family to it, and can on,y offer the advice of please be aware before taking such a trip.