Congrats on winning the entry. It’ll be one of the coolest experiences you’ve ever done. I did the swim last year with the Zoot Zenith wetsuit and 2 swim caps (one silicone and one neoprene) and was perfectly fine. Can’t agree more that silicone earplugs are very helpful. You will be cold upon entry into the water, but that goes away after 5 minutes of swimming. The most important thing to this swim is making sure you don’t swim directly toward your destination. Understanding the currents beforehand is key. Be sure to attend the race meeting beforehand and they’ll share with you sighting locations and other things to consider. I bought a dvd (Lane lines to shore lines) authored by one of the swim directors (Gary Emich) prior to the race and it was a great help. He includes a section completely dedicated to swimming Alcatraz and I felt it to be invaluable.
Enjoy the experience!
http://www.lanelinestoshorelines.com/ssp/store