Snorkel- A snorkel is a tube, typically made of plastic, running from the air-box and CVT or transmission intake, which extends higher than the standard heights of these intakes. It allows the ATV to operate in deeper water without sucking water into the motor or transmission.
On the Trail- A snorkel is necessary only if you intend to ride in deep water and mud. If you intend to cross deep streams, or ride in deep mud bogs, then a snorkel is a modification that is a must. There are many snorkels that you can buy from manufacturers, or you can make one of your own.