CROSSING (Port Approach)
When two power-driven boats cross paths, it is the boat approaching on the portleft hand side of a vessel. side that is the give-way vessel.
So, if you are Vessel A in this example, then you are the give-way vessel and you must take early and substantial action to avoid crossing the path of Vessel B, which is the stand-on vessel.
As Vessel A, you should let Vessel B know your intention by blowing one short blast and then turning to starboardright hand side of a vessel. to get out of the way. Vessel B will then blow one short blast indicating that it understands and will maintain its course.