Watercross consists of crossing water while riding a snowmobile, which is possible because snowmobiles have wide tracks for traction and flotation in the snow. If one hits the water at an acceptable speed (5 mph per 150 lb or 12 km/h per 100 kg of weight) and keeps the sled's throttle open, the track keeps the snowmobile on the surface of the water without sinking. If the rider backs out of the throttle or the sled bogs or floods out, the sled will sink. A sunk sled is able to be revived by cleaning water out of the carburetor, exhaust, spark plugs, and replacing the fuel. The front of the sled is pitched upwards like riders commonly do in deep mountain powder snow.
The Grantsburg, Wisconsin first annual World Championship Snowmobile Watercross was held in July 1977 and it has been held annual on the third week of July since. The first race was simply held to see who could make it the 300 feet (91 m) from the island on Memory Lake to the shore. Most didn't, but the winner did go about 500 ft (150 m). In the years following, racers became more skilled and the machines more powerful. Today they race both drags and ovals with an eight-lap championship run. Over 100 racers compete in the various classes. The Classes range from the beginners' Stock Drags to the top Pro-Open Ovals Class. Competitive watercross is run by two main circuits. The IWA (International Watercross Association) operates mainly in the Midwest, while the EWA (Eastern Watercross Association) operates in the Northeastern States. 
In most cases, participants in watercross strip their snowmobiles of all non-essential parts—including the seat—in order to save weight.
Watercross competitions are held during the summer and the participants wear life jackets, and have a buoy tethered to their sleds. If for some event the rider and sled do not complete the course, the rider releases the buoy from the snowmobile so that it floats to the surface and marks the sled for retrieval. Watercross competitions, as with any other motor sports, have ambulance and rescue crews nearby in the event of an accident.
While it is possible to skim over the water with a stock snowmobile, the practice is dangerous and illegal in some states in the USA. In February 2006, a Massachusetts man died in New Hampshire after sinking into the water during a failed skimming attempt. In July 2010, a 40-year old man died in Anaktuvuk Pass while attempting to skim across Eleanor Lake. The practice of "skimming" is illegal in Minnesota and New Hampshire. In Wisconsin, there are places where skimming is encouraged, and some businesses rely on it to attract customers, for example at Bauers Dam in Conover, Wisconsin.
- "Skip the snowmobile skipping: Stay clear of thin, open ice". Science Buzz / National Science Foundation). Retrieved 5 December 2010.
- Glauber, Bill (July 18, 2009). "On solid or liquid, give it the gas". Milwaukee Journal Sentinel. Retrieved 5 December 2010.
- Boettcher, Troy. "Grantsburg 2009 – From the Insid". Max Sled. Retrieved 5 December 2010.
- "Snowmobile Watercross Racing Photos". SnowRider Magazine. Retrieved 5 December 2010.
- "Finish man sets world record after driving 180km over water on a snowmobile". July 25, 2013.