Have observed that vehicle wheels continue to turn in water, although on occasion some wheels are turning counter to others. Landing gently on these wheels seems to increase the likelihood of becoming trapped, even with the rotors still turning in the water.
Drive into water until the vehicle is fully swimming and note the direction and speed of spinning wheels. They will rarely be consistent so some number of trials may be needed. Try to land gently on wheels turning opposite your direction of motion.
Front wheels tend to want to spin in reverse. Rear wheels almost always spin forwards. I find it more likely to become stuck slowly backing out of water. Wheels do not respond to control inputs. Sound of screeching breaks sometimes audible as vehicle becomes stuck, unstuck, or exits the water. Even on a successful landing some wheels resist vehicle motion until it transitions to land mode.