You ONLY display ALFA if the boat is restricted in its ability to maneuver as a consequence of diving operations.
You technically SHOULD NOT display it if you are ANCHORED. In that case you are NOT restricted in your ability to maneuver because you have divers in the water - you are restricted because you are made fast to the seabed with your ground tackle! I understand the argument for flying ALFA if you're anchored with divers below, and often do it myself simply due to convention, but if you want to be technically correct about it the proper thing to fly in such a situation is an anchor ball.
TECHNICALLY the diver-down flag should be with the DIVERS too, not the boat. That is, the divers should tow or otherwise take the flag with them and secure it either to themselves or directly (or as nearly as possible) over their location. The argument for it being on the boat is that it can be displayed much higher off the water and thus is more visible. This only helps if the divers are reasonably close to where the flag is!
A boat that has FREE SWIMMING divers below is NOT ordinarily restricted in its ability to maneuver as a consequence of the divers being in the water. It arguably is WHILE discharging or picking them up (since propulsion would ordinarily have to be secured), but not while sitting. If it is unable to maneuver due to being anchored then it should be flying an anchor ball or, at night, proper anchor lights.
I understand the USCG has given dispensation to dive operators in some parts of Florida who drift dive to fly ALFA since they end up effectively using their boats as a SHIELD against other boats who would otherwise run over the diver's flag, but that's a special case and frankly points to the insanity and lack of concern of other people on the water. That operators are having to maneuver to use their vessels as shields to keep people from buzzing dive flags and running over people in the water is a pretty sad commentary on the knowledge and intelligence of people operating boats these days.
The specific cite is:
http://www4.law.cornell.edu/uscode/33/2027.html
Note the HEADING -
"Vessels not under command or restricted in their ability to maneuver Rule 27 "
A VESSEL is not engaged in diving operations with free divers below. It IS if they are tethered to the vessel in some way (e.g. surface supplied air or communications as with most commercial diving operations, a deco bar below the vessel, etc)
I know this sounds pedantic but it isn't. Abuse and misuse of signalling conventions, including flags and dayshapes, is a serious problem and frequently contributes to collisions.
While displaying an ALFA when you really shouldn't isn't likely to cause a collision with your boat, it might contribute to one between other vessels in the area, and if you are improperly displaying (or not displaying!) shapes and lights you are likely to be found at least partially responsible for the incident if this is the case. If you have an ALFA up but NOT an anchor ball you could conceivably get tagged for partial responsibility for the collision if you are in fact anchored and someone runs into you.
If you read without context (as the YMCA and some others appear to have done here) you might think you can be trolling for fish with lines astern and display opposed cones during the day to claim "fishing" privilege under Rule 26. You'd be wrong. The test for a vessel claiming privilege under the navigational rules is that your maneuverability must be substantially impacted by the operation in question to the point that obeying the rules of the road - that is, not claiming the privilege - would cause harm to the vessel. That it would be inconvenient[/b] to maneuver doesn't pass the test.
This is the basis for all claims of privilege under the rules of the road, both COLREGS and Inland, in the fundamental hierarchy of vessels and specific exemptions or claim of privilege.
Read the whole thing (either); you'll find that the rules are designed so that there has to be at least two violations before there is a collision. This is an intentional feature of the rules, and means that it is very, very rare for either vessel to completely escape responsibility when contact occurs.
You technically SHOULD NOT display it if you are ANCHORED. In that case you are NOT restricted in your ability to maneuver because you have divers in the water - you are restricted because you are made fast to the seabed with your ground tackle! I understand the argument for flying ALFA if you're anchored with divers below, and often do it myself simply due to convention, but if you want to be technically correct about it the proper thing to fly in such a situation is an anchor ball.
TECHNICALLY the diver-down flag should be with the DIVERS too, not the boat. That is, the divers should tow or otherwise take the flag with them and secure it either to themselves or directly (or as nearly as possible) over their location. The argument for it being on the boat is that it can be displayed much higher off the water and thus is more visible. This only helps if the divers are reasonably close to where the flag is!
A boat that has FREE SWIMMING divers below is NOT ordinarily restricted in its ability to maneuver as a consequence of the divers being in the water. It arguably is WHILE discharging or picking them up (since propulsion would ordinarily have to be secured), but not while sitting. If it is unable to maneuver due to being anchored then it should be flying an anchor ball or, at night, proper anchor lights.
I understand the USCG has given dispensation to dive operators in some parts of Florida who drift dive to fly ALFA since they end up effectively using their boats as a SHIELD against other boats who would otherwise run over the diver's flag, but that's a special case and frankly points to the insanity and lack of concern of other people on the water. That operators are having to maneuver to use their vessels as shields to keep people from buzzing dive flags and running over people in the water is a pretty sad commentary on the knowledge and intelligence of people operating boats these days.
The specific cite is:
http://www4.law.cornell.edu/uscode/33/2027.html
Note the HEADING -
"Vessels not under command or restricted in their ability to maneuver Rule 27 "
A VESSEL is not engaged in diving operations with free divers below. It IS if they are tethered to the vessel in some way (e.g. surface supplied air or communications as with most commercial diving operations, a deco bar below the vessel, etc)
I know this sounds pedantic but it isn't. Abuse and misuse of signalling conventions, including flags and dayshapes, is a serious problem and frequently contributes to collisions.
While displaying an ALFA when you really shouldn't isn't likely to cause a collision with your boat, it might contribute to one between other vessels in the area, and if you are improperly displaying (or not displaying!) shapes and lights you are likely to be found at least partially responsible for the incident if this is the case. If you have an ALFA up but NOT an anchor ball you could conceivably get tagged for partial responsibility for the collision if you are in fact anchored and someone runs into you.
If you read without context (as the YMCA and some others appear to have done here) you might think you can be trolling for fish with lines astern and display opposed cones during the day to claim "fishing" privilege under Rule 26. You'd be wrong. The test for a vessel claiming privilege under the navigational rules is that your maneuverability must be substantially impacted by the operation in question to the point that obeying the rules of the road - that is, not claiming the privilege - would cause harm to the vessel. That it would be inconvenient[/b] to maneuver doesn't pass the test.
This is the basis for all claims of privilege under the rules of the road, both COLREGS and Inland, in the fundamental hierarchy of vessels and specific exemptions or claim of privilege.
Read the whole thing (either); you'll find that the rules are designed so that there has to be at least two violations before there is a collision. This is an intentional feature of the rules, and means that it is very, very rare for either vessel to completely escape responsibility when contact occurs.
