What does it mean by Precautions required by good seamanship or special circumstances @ Rule2 COLREG
Some examples of precautions that may be required by the ordinary practice of seamen, or by special circumstances, are the following:
A vessel underway would be expected to keep clear of a vessel at anchor as a matter of seamanship. But a vessel underway and stopped must not rely on other vessels keeping out of her way, unless she is not under command and is displaying the appropriate signals; she must comply with the Rules.
When a vessel anchors she must do so without endangering other vessels which may be navigating close by. She must not anchor too close to other anchored vessels. Sufficient cable must be put out according to circumstances and a second anchor should be used if necessary.
In dense fog, a vessel without operational radar may not be justified in being underway at all but should anchor if it is safe and practicable for her to do so.
When two vessels are approaching one another at a difficult bend in a tidal river it has been held to be the duty of the one having the tide against her to wait until the other has passed
The effects of shallow water must be taken into account. A vessel moving at fairly high speed through the water produces pressure fields that become much greater when water flow around the ship is restricted. There is a reduction of pressure beneath the ship which causes bodily sinkage so that the vessel is said to "squat" in the water. In addition to an increase in mean draught, there will usually be a change of trim, by the bow or stern according to the circumstances. When the depth of water is less than about one and a half times the draught this effect is much more pronounced. If there is shallow water on only one side, the pressure fields may cause the ship to sheer away from the bank, bringing danger of collision if another vessel is passing close by. Interaction between ships due to the pressure fields will also be greater in shallow water and the steering qualities are likely to be affected
Rule 10 only applies to traffic separation schemes adopted by the Organization. Before adoption by IMO, a scheme must be approved by the Maritime Safety Committee. However, a Government may in urgent cases implement a new scheme or an amendment to an adopted scheme before receiving IMO approval. If the scheme applies to international waters compliance would not be compulsory for the ships of all nations but it would be good seamanship to comply with the provisions of Rule 10.