A vessel of less than 12 meters in length, when aground, shall not be required to exhibit the lights or shapes prescribed in subparagraphs (d)(i) and (ii) of this Rule.
A vessel of less than 20 meters in length, when at anchor in a special anchorage area designated by the Secretary, shall not be required to exhibit the anchor lights and shapes required by this Rule.
Small craft less than 7 meters in length are not required to show an anchor light or shape if anchored out of the way of all other water traffic. Larger vessels must comply with Rule 30 wherever anchored, this includes the showing of a "anchor ball" dayshape.
Any vessel at anchor may, and vessels of 100 or more meters in length must, show deck or working lights to increase her visibility to other vessels. A vessel made fast to a mooring is "at anchor." A vessel dragging its anchor is not "made fast to the bottom" and, is not a vessel at anchor, but a vessel underway.
The Inland Rules only provide for "special anchorage areas" in which anchor lights and shapes are not required for craft less than 20 meters in length. These are generally established off marinas and yacht clubs where boats are left unmanned on moorings for days at a time and electric power is not available for showing anchor lights. There is no provision in the International Rules for areas where anchor lights and shapes are not required.
International Rule 30(d) requires vessels of 12 meters or more in length when aground to show the three "anchor balls" day signal or two all-round red lights at night, few small craft are equipped to meet this requirement, and most fail to comply. The Inland Rules have the same requirement, but add "if practicable" without defining the limits of practicability. A vessel is not considered "aground" for the purposes of this Rule if she is intentionally placed in contact with the bottom or against the bank to hold her position, in this case, the vessel is underway with no way on.