There are two entry level Captain licenses that the Coast Guard will issue to mariners; the OUPV and the Master 100 tons or less.
The OUPV (Operator of Uninspected Passenger Vessel) license authorizes the mariner to carry six or fewer passengers (AKA 6-pack) on vessels of less than 100 GRT (about 65 feet). The sea service requirements are 360 days experience in the operation of vessels; if 90 days of this experience was on ocean waters you can request a near coastal route (valid on all Inland waters and on ocean water 100 miles offshore), otherwise the license will be limited to all federally navigable Inland water of the US. This is the most common license held by fishing guides.
The Master 100 ton or less license authorizes the authority to operate vessels carrying more than six passengers, cargo vessels, supply boats, crew boats, and other types of vessel (excluding towing vessels) within the authority of the license. This license will be issued as Inland or Near Coastal and with tonnage limitations of 25, 50, or 100 tons. This license is required to operate charter boats carrying more than six passengers.
- An Inland route requires 360 days of experience on the deck of a vessel. A Near Coastal route requires 720 days experience on the deck of a vessel; at least 360 days of this experience must be on ocean waters.
- The tonnage limitation issued will be based on the size of vessels that the qualifying experience was on. If all the experience was on state registered boats less than 5 GRT the applicant will be issued a 25 ton limitation; if any of the experience was on a documented vessel greater than 5 GRT the applicant will be issued a 50 ton limitation; to qualify for a 100 ton limitation the applicant must document either 25% of the experience on vessels greater than 50 tons (90 days for an Inland route or 180 days for a Near Coastal route) OR 50% of the experience on vessels greater than 34 tons (180 days for an Inland route or 360 days for a Near Coastal route).
Gross Registered Tons (GRT) is not a measurement of a vessels weight, but of the volume of space within the hull. Each 100 cubic foot of space is equal to one GRT. The GRT of a documented vessel will be recorded on the Certificate of Documentation issued by the Coast Guard. On state registered boats the GRT can be estimated using this formula: (L x B x D) / 100 where L is the deck length of the vessel inside the hull; B is the breath of the vessel measured from side to side along the deck inside the hull; D is the depth of the hull measure from the top of the gunnel to the chine. Multiple these three values together and divide the answer by 100.