The U.S. Coast Guard issues two main types of professional captain’s licenses for recreational mariners: the Operator of Uninspected Passenger Vessels (OUPV) or “six-pack” license, and the Master’s license, which comes in 25-, 50-, 100-, and 200-Ton varieties. The OUPV license allows you to carry up to six paying passengers on uninspected vessels up to 100 gross tons. The Master’s license enables operation of both inspected and uninspected vessels, with the ability to carry seven or more paying passengers.