It was my first time with wife and 2 kids, and the crew on the boat was very friendly and gave us a quick overview on snorkeling 101 (and this is coming from someone who has never seen one in person) which was super useful to get you started. They also had pool noodles that can be inserted into your floatation vest, to help you stay afloat.
I have zero swimming skills, yet I was in the ocean for about 10-15 minutes, so do not worry if you are worried about your swim skills. Overall it was a great experience!