The chart below summarizes a portion of the FCC rules --47 CFR 80.371(c)and 80.373(f)
Type of Message Appropriate channel(s)

DISTRESS SAFETY AND CALLING -Use this channel to get the attention of another station (calling)or in emergencies (distress and safety).16

INTERSHIP SAFETY -Use this channel for ship-to-ship safety messages and for search and rescue messages and ships and aircraft of the Coast Guard.6

COAST GUARD LIAISON -Use this channel to talk to the Coast Guard (but first make contact on Channel 16).22

NONCOMMERCIAL -Working channels for voluntary boats.Messages must be about the needs of the ship.Typical uses include fishing reports, rendezvous, scheduling repairs and berthing information.Use Channels 67 and 72 only for ship-to-ship messages.
9(fn6),68,69,71,72,78,
79(fn4),80(fn4)

COMMERCIAL -Working channels for working ships only.Messages must be about business or the needs of the ship.Use channels 8,67,72 and 88 only for ship-to-ship messages.
1(fn5),7,8,9,10,11,18,
19,63(fn5),67,72(fn7),
79,80,88(fn1)

PUBLIC CORRESPONDENCE (MARINE OPERATOR)-Use these channels to call the marine operator at a public coast station.By contacting a public coast station,you can make and receive calls from telephones on shore.Except for distress calls,public coast stations usually charge for this service.
24,25,26,27,28,84,85,
86,87,88(fn2)

PORT OPERATIONS -These channels are used in directing the movement of ships in or near ports,locks or waterways.Messages must be about the operational handling movement and safety of ships.In certain major ports,Channels 11,12 and are not available for general port operations messages.Use channel 20 only for ship-to-coast messages.Channel 77 is limited to intership communications to and from pilots
1(fn5),5(fn3),12,14,20,
63(fn5),65,66,73,74,77

NAVIGATIONAL -(Also known as the bridge-to-bridge channel.)This channel is available to all ships.Messages must be about ship navigation,for example,passing or meeting other ships.You must keep your messages short.Your power output must not be more than one watt.This is also the main working channel at most locks and drawbridges.
13,67

MARITIME CONTROL -This channel may be used to talk to ships and coast stations operated by state or local governments.Messages must pertain to regulation and control, booting activities,or assistance to ships.
17

DIGITAL SELECTIVE CALLING -Use this channel for distress and safety calling and for general purpose calling using only digital selective calling techniques.70

WEATHER -On these channels you may receive weather broadcasts of the National Oceanic and Atmospheric Administration.These channels are only for receiving.You cannot transmit on them.
Wx-1 162.55
Wx-2 162.4
Wx-3 162.475

Footnotes to table
1.Not available in the Great Lakes,St.Lawrence Seaway,or the Puget Sound and the Strait of Juan de Fuca and its approaches.
2.Only for use In the Great Lakes,St Lawrence Seaway,and Puget Sound and the Strait of Juan de fuca and its approaches.
3.Available only In the Houston and New Orleans areas.
4.Available only in the Great Lakes.
5.Available only In the New Orleans area.
6.Available for Intership,ship,and coast general purpose calling by noncommercial ships.
7.Available only In the Puget Sound and the Strait of Juan de Fuca.

wireless.fcc.gov/marin...chanl.html Get the list here.