I just returned from the Magic on 1/26 (missing it already) and I ordered the Safe Sea product over the Internet.
It comes with your choice of SPF 15, SPF 30, or no SPF at all.
It's difficult to say for sure if it indeed kept the Sea Lice away from us. We applied it in the cabin before we left the ship so it would be sure to be in place, and the label says at least 10 minutes before going in the water.
The only place we went into the water was at
Castaway Cay, which is the night before you disembark, so we didn't have that much contact with other guests that didn't use it. I don't know of anyone that said they did have it. I do know that there was a man at Guest Services the evening after we left St Thomas asking if they knew anything about a red rash and that he would visit the Medical Center the next morning.
There have been other cruisers in the last 2 or 3 weeks that have said on this board that they encountered a rash after swimming.
I considered it to be inexpensive insurance. It cost me $12.95 for a 4 ounce bottle, plus shipping. Personally, I'm going to keep using it every time I cruise to that area.
The official season for Sea Lice in the Atlantic is from March to August. It's also a huge ocean and I wonder just how accurate the timing would be.