You're in luck. There is a shower on TI. It may be a little cold, but you can still rinse off. You can snorkel off TI, but you will have to bring your own gear. They will not let you use the gear they have. Also, depending on the time of year, there can be a lot of sea urchins close to shore. Once you are beyond that, and you're floating, it shouldn't be a problem. There is also some coral that my be just under the water level, so be mindful of that. There have been people that snorkel there.