The Rule of Twelfths provides navigators with a method of estimating the rate of regular tidal flows
Navigation - how to find your way by sea
The safest way to sail westbound across the Atlantic is to get your timing right and follow the trade winds.
Where ships and other vessels converge the risk of collision becomes high. To minimise this risk larger vessels are obliged to stay within defined channels. Smaller craft also have their obligations.
Mariners can be confused by differences in navigation buoys worldwide.
AIS gives useful warning of the approach of other vessels
The Collision Regulations apply to all mariners. But some believe they can be abused.