The 8th day of Hawaii I spent the day doing snorkeling activities. This is a good read to remember what I learned:

http://travel.johnmatienzo.com/?p=1276

Also, one additional tip is if you want to take pictures underwater, it would have been good to invest in this (this is what Janie did): https://www.amazon.com/Best-Sellers-Cell-Phone-Dry-Bags/zgbs/wireless/17875443011

In terms of snorkeling while you’re on a Kayak, you can easily go on and off without actually tipping the kayak over. For going off, put your snorkeling mask on first properly and tightly (remember to wash your face from the sunscreen), and then quickly “sit” on the edge and slide off. Then put your flippers while you’re in the water. Note, if you want to wear a life jacket, put it on and tighten it before you get into the water. Personally, the mobility is extremely limited with a life jacket, but it does make it easier/less tiring if you’re out for a long time.