Hopefully as you spend more time in a squirtboat it will get easier to balance in. One of the keys to this is maintaining a neutral position with your upperbody. In Tupperware, that position is always the same. In a squirtboat, it is always different but can be easy to find with a little practice. The neutral position is the balance point which maintains your angle in both horizontal and vertical planes. As you practice freestyle moves and your boat moves through the vertical plane always try to stay in the neutral position. Eventually, your body will automatically find this position and you will become a very efficient squirtboater.