Hey There! Chris here!
My kids' favorite thing to do on a boat is go on the back swim platform and open the back storage compartment that doubles as their toy box on the water. The trunk is full of noodles, bubbles, squirt guns, rafts and my daughter’s favorite, the water balloon launcher.
My kids, however, are not the only ones who love to dig through the trunk. It is not unheard of to see two of my buddies on the bow of the boat having a squirt gun fight. 
Here are some pictures of kids enjoying a great summer day.
When we go out to the sand bar for the day, my daughter reminds me that we have to take the two Lanai Islands, which we tow behind the boat. The Lanai Islands double as a great place to take a nap when the kids are not using it as a trampoline. This year my wife is bugging me to get a real trampoline and slide.
Every once in a while I will place the kids in the tube with the sand pales and walk up to the shoreline where we build sand castles. The beach party doesn't last too long though, as they want to be back on the boat.
What is your favorite toy and why? Would love to hear from you!