Regarding "Tensing Pen", the answer is no. Awesome resort for sure but for registered guests only. If you want to snorkel, you could head up to the lighthouse area. There is a wooden ladder there but it is a long one. For me, it is a little too high and I get spooked but my husband heads right down it and doesn't look back. LOL

Also, during the day, Ricks is a nice place to hang out and snorkel with easy access. The good thing about it is that it is not crowded during the day. Plus, the view is phenomenal! Around 4 or so, the bus loads start heading up. You can't bring a cooler in but we have found it a nearby place to snorkel. If you buy a drink or maybe some appetizers you're cris!

Generally speaking, Xtabi would be on my top list of "friendly" places to hang out and snorkel. Again, buying drinks or food while enjoying their establishment is only fair. Just grab a route taxi after you walk down Seastar Lane and you will be good to go. 100J per person which is quite reasonable to me. Remember...red plates on the route taxi's! Enjoy!