Reference

US VHF marine channel reference

The channels you actually need to know as a recreational boater in US waters. Monitor 16 whenever the radio is on, and use a working channel for everything else.

ChUseNotes
16Distress, safety, hailingMonitor at all times. Initial contact, then switch.
9Alternate hailing (non-commercial)Reduces traffic on 16 in busy areas.
13Bridge-to-bridge (ships)Low power. Required for vessels >20m near commercial traffic.
06Intership safetySearch and rescue coordination between vessels.
22AUSCG liaisonUSCG asks you to switch here from 16 for non-emergency comms.
67Commercial / bridge (lower Mississippi)Regional commercial working channel.
68Recreational workingMarina, dockmaster, club racing chatter.
69Recreational workingCommon alternate.
71Recreational workingCommon alternate.
72Non-commercial intershipBoat-to-boat conversation.
78ARecreational workingCommon in the Northeast and Florida.
WX1–WX10NOAA weatherContinuous weather broadcast. Receive only.

Source: USCG and FCC marine channel assignments. Channel availability varies in Canada, the Great Lakes, and international waters.