Avoid Impeding Vessel Constrained by Draught (Rule 18(d))

Chart overlay shows a narrow DREDGED APPROACH CHANNEL (blue, ~0.8 NM wide, dredged to 15 m) with wider water around it (stippled, 57 m). Your draught is 3.0 m you have plenty of margin in the 5+ m area outside the channel. Lateral buoys mark the edges (IALA Region A, inbound from the north): RED cans on the east edge (port-hand for inbound), GREEN cones on the west edge (starboard-hand for inbound).

The CBD target ahead is a deep-draught vessel signalling "Constrained by Draught" (badge "C", Rule 28). Her keel sits only a metre or two off the dredged bottom she cannot leave the dredged channel without grounding and cannot alter sharply without losing steerage.

Rule 18(d): every vessel, other than a vessel not under command or restricted in ability to manoeuvre, shall AVOID IMPEDING the safe passage of a vessel constrained by her draught. "Impeding" means forcing her to take avoiding action. You CAN safely leave the channel 5 m under a 3 m keel is ample. Do so EARLY so she never has to alter her line. Keep CPA 0.5 NM.