Our son built one of these a couple of years ago. He took a big igloo cooler with wheels that had a place to put a divider in. Cut a clear cutting board to fit and sealed it in place. Put a gel cell in the dry half along with a car stereo through the top (bluetooth and charging port too) and two waterproof speakers in the sides. Put led lighting inside too.
His was a hit on the river float they did and he uses it on his patio too. Easy to find the beer with the led light inside.