I know the last thing anyone wants to do in California at the moment is get into a pool! But, one of my favourite ways of keep cool in the summer and working on my core.
The trick of this move is to keep your core pulled in tight and your spine nice and tall. If you do not activate these muscles, you will fall off the kickboard.
Sculling - Kickboard Sit - GoSwim!
I am particularly fond of this move when visiting hotels in Mexico. For some reason, they build their pools at a standard depth of 4'10" ... being 4'11", it means I am submerged if I stand vertically. This kickboard move allows me to stay in the pool and not bob up and down like a drowning rat!