The common sense idea, is you should stop, get out and try to guage the depth of the water. If in doubt turn around and go another route, especially if your not familiar with the area
If you choose to proceed, enter the water in a low gear, idealy 1st or 2nd at crawling pace. Speed up to 5mph once you have entered creating a bow wave, the exhaust gasses will stop the water entering your engine and remember a foot of water is enough to float your car down stream. Keep that engine rev’s high even slipping the cluch high and what ever you do do not stall.
If in doubt fit a snorkel, a back flow device or raised exhaust extention ?