1.10 Responsibilities Between Vessels (Rule 18)

Rule 18 — The Pecking Order (When In Sight)

Rule 18 answers a different question from Rules 13–15. Geometry rules ask where is the other vessel relative to me? Rule 18 asks what kind of vessel is she? and assigns keep-out-of-the-way duties by status. It applies to vessels in sight of one another (Rule 11 gate) and is expressly subject to the exceptions in Rules 9, 10, and 13 — narrow channels, traffic separation schemes, and overtaking can override the hierarchy.

For Master 100 Q100 (90%), memorize the order as a ladder from most privileged / least maneuverable down to ordinary power-driven traffic — then place seaplanes and WIG craft as special cases at the bottom of the keep-clear chain.

Classic Hierarchy (Exam Ladder)

Except where Rules 9, 10, and 13 otherwise require:

Memory phrase used by many Masters: "New Reels Catch Fish So Purchase Some" is optional; the statutory ladder is what Q100 grades: NUC > RAM > fishing > sailing > power-driven, with CBD and seaplane/WIG layered carefully.

Power-Driven Duty (Your Default as Master 100)

A power-driven vessel underway shall keep out of the way of:

1. a vessel not under command;
2. a vessel restricted in her ability to maneuver;
3. a vessel engaged in fishing;
4. a sailing vessel.

Nearly every Master LT 100 passenger vessel is power-driven on the job. In open water, in sight, with no Rule 13/9/10 override, you keep clear of pure sail, true fishing gear that restricts maneuverability, RAM work, and NUC casualties. Passenger count creates no special privilege.

Classification Traps That Flip Rule 18

• Sail under power is power-driven (Rule 3) — no sail privilege.
• Trolling lines do not make a vessel "engaged in fishing" — she remains ordinary power-driven.
• Overtaking (Rule 13): any vessel overtaking any other keeps clear — a sailboat overtaking your power-driven passenger vessel must keep clear despite ordinary sail-over-power logic.
• Narrow channel / TSS (Rules 9–10): small craft, sail, and fishing shall not impede channel-bound or lane-following power-driven vessels that cannot leave the deep water. Rule 18 does not authorize a sailboat to block a freighter in the ship channel.

Sailing and Fishing Layers

A sailing vessel underway shall keep out of the way of NUC, RAM, and fishing. Sail is not at the top of the pyramid; she only sits above power-driven traffic.

A vessel engaged in fishing when underway shall, so far as possible, keep out of the way of NUC and RAM. Fishing privilege over power and sail is real, but fishing does not trump a casualty vessel or a vessel restricted by the nature of her work.

Constrained by Draft — International Only (Hard Inland Difference)

Under International Rules (Rule 18(d)):

• Any vessel other than NUC or RAM shall, if the circumstances of the case admit, avoid impeding the safe passage of a vessel constrained by her draught exhibiting Rule 28 signals (typically three all-round red lights in a vertical line by night; a cylinder by day).
• A CBD vessel shall navigate with particular caution having full regard to her special condition.

Inland Rules have no Constrained-by-Draft category. There is no CBD pecking-order slot and no Rule 28-style CBD light/shape duty under Inland. Master candidates who operate only on rivers sometimes invent "deep draft privilege" inland and lose the point; coastal Masters who forget CBD exists seaward of the demarcation line also lose points.

CBD is not RAM: CBD is draft vs available depth/width (International); RAM is the nature of the work.

Seaplanes and WIG Craft

• A seaplane on the water shall, in general, keep well clear of all vessels and avoid impeding their navigation. If risk of collision exists, she still must comply with the Rules of Part B.
• A WIG craft, when taking off, landing, and in flight near the surface, shall keep well clear of all other vessels and avoid impeding their navigation. When operating on the water surface, a WIG craft complies with the Rules of this Part as a power-driven vessel.

Exam takeaway: do not place seaplanes above NUC/RAM in a false hierarchy, and do not treat surface WIG craft as aircraft free of power-driven duties.

Master Scenario: Passenger Vessel Meets Mixed Traffic

You run a 49-passenger near-coastal T-boat (power-driven) seaward of the COLREGS Demarcation Line:

1. Pure sailing yacht on a crossing geometry with risk of collision → you keep clear (Rule 18 + Rule 15/16 as applicable).
2. Trawler streaming nets that restrict maneuverability → you keep clear as power vs fishing.
3. Sportfisher trolling with light lines only → no fishing privilege; apply ordinary power-vs-power geometry rules.
4. Dredge showing RAM signals → you keep clear of RAM.
5. Deep-draft freighter showing three red all-round lights (CBD, International) → avoid impeding her safe passage when circumstances admit; she must still navigate with particular caution.
6. Same freighter inside the demarcation line (Inland) → no CBD category; apply ordinary Inland steering rules and any channel/TSS duties.
7. Sailing yacht overtaking you from the stern → she keeps clear under Rule 13 despite sail-over-power.

Rule 18 vs Geometry — How to Decide on Exam Stems

1. Are the vessels in sight? If not (radar-only fog), go to Rule 19, not Rule 18 hierarchy.
2. Is the situation overtaking? Rule 13 overrides hierarchy for the overtaking vessel's keep-clear duty.
3. Are you in a narrow channel or TSS with shall-not-impede language? Rules 9/10 can require small craft/sail/fishing not to impede deep traffic even when Rule 18 would favor them in open water.
4. Otherwise, apply Rule 18 status, then use Rules 14–17 geometry and give-way/stand-on duties among vessels of the same effective class.

Exam Framing for Q100 (90%)

Lock: NUC > RAM > fishing > sailing > power-driven; power keeps clear of those four; CBD International only; Rules 9, 10, 13 override; seaplanes/WIG generally keep well clear; trolling is not fishing; sail under power is power. Master passenger stems almost always cast you as power-driven near the bottom of the ladder — answer from hierarchy plus the override rules, not from "I have more passengers."