difference between “Ship” or “Vessel” in law of the sea, LOSC and customary international law

A “ship” or “vessel” is a concrete physical object, but that does not mean we can satisfactorily define it. Here, the difficulty is that the legal context in which the word “ship” is used vary so significantly that it may be inappropriate to specify one definition.

Drafters and decision makers have struggled with the problem of defining “ship” in national and international law. In a British case involving insurance policy coverage, the lower court had found that a crane floating on pontoons was not a “ship” or “vessel.” On appeal Lord Justice Scrutton was troubled by the lack of a definition of those terms:
One might possibly take the position of the gentleman who dealt with the elephant by saying he could not define an elephant, but he knew what it was when he saw one, and it may be that is the foundation of the learned Judge’s judgment [in the court below], that he cannot define “ship or vessel” but he knows this thing is not a ship or vessel. I should have liked to be able to give a definition here, because … it is rather a pity that the Courts are not able to give a definition of the words which are constantly turning up in a mercantile transaction. But the discussion today … of the various incidents and various kinds of things to which the words “ships or vessels” [have] been applied, has convinced me that it is of no use at present to try to define it, and the only thing I can do in this case is to treat it as a question of fact and to say that I am not satisfied that the learned Judge was wrong.
We assuredly can say more about the concept of “ship” or “vessel” than “I know one when I see one,” but it does not necessarily follow that an all-encompassing definition is essential to that end. The ABILA LOS Committee initially proposed the following definition for UNCLOS:
“Ship” [and] “vessel” have the same, interchangeable meaning in the English language version of the 1982 LOS Convention. “Ship” is defined as a vessel of any type whatsoever operating in the marine environment, including hydrofoil boats, air-cushion vehicles, submersibles, floating craft and floating platforms. Where, e.g., “ship” or “vessel” is modified by other words, or prefixes or suffixes, as in the Article 29 definition of a warship, those particular definitions apply.
I fear that this definition, or any one definition proposed for use in UNCLOS, may be either too broad or too narrow, depending on the context in which it is used. Interpretation of “ship” may well vary from issue to issue, and when we seek a definition that applies to as wide a range of situations and issues as does UNCLOS, it becomes particularly difficult to agree on an acceptable definition.
Before I explore my concerns with the proposed definition, let me note that there is much in the definition with which I agree.

First, I agree that particular subcategories of ships may need to be addressed separately. This is certainly true of warships, the subject of UNCLOS Article 29. My comments do not address warships.

Second, I agree that “ship” is a general term, referring to a variety of different craft. There was a time in the age of sail when “ship” may have had a relatively specific and determinant meaning. A “ship” was “a vessel with three or more masts and fully square-rigged throughout.”
A “ship” was thus distinguishable from smaller craft; a “ship” was not a brig, a schooner, or a cutter. Today, however, the connotation of “ship” is not so specific.

Third, I agree that the terms “ship” and “vessel” should be equated. As has been noted, the terms were viewed as identical at UNCLOS III. Use of different terms in the UNCLOS English language version came about because two different committees at the Conference worked on different articles; one committee used “ship” in its articles, and the other used “vessel.” This point suggests the need for a technical change in the proposed definition. The word “vessel” in the second sentence should be changed, because if “ship” and “vessel” are synonyms, then the sentence in effect reads, “Vessel is defined as a vessel …”
It would be better to substitute a phrase like ‘Ship’ or ‘vessel’ is defined as a device capable of traversing the sea .…”
The critical issue, though, is whether we can arrive at any sensible definition capturing all the various types of craft and all the different purposes for which we have international legal rules related to ships. With respect to types of craft, the concern with whether a definition is suitable is likely to occur at the margins.

All will agree that an oil tanker, navigating the high seas under its own power and exposed to maritime risks, is a “ship” or “vessel.” But, with respect to various issues, should we include as ships: floating platforms or drilling rigs (with or without engines), temporarily fixed platforms, hydrofoils, seaplanes on the water, amphibious craft, submersibles, very small boats, houseboats or docked hotels like Queen Elizabeth I, boats towed for repairs, abandoned craft, wrecks (capable of being raised or not), craft in drydock for repair or safekeeping, craft under construction (launched or yet to be launched)? If we all could agree on what to include or exclude as a ship or vessel in all cases, drafting challenges arise. For example, the initial proposed definition indicated a preference to exclude fixed platforms from the category of “ship.” Yet the proposed definition, which encompasses “a vessel of any type whatsoever operating in the maritime environment,” may be ambiguous in this regard, unless the word “including” is read as a term of limitation rather than a term of illustration, i.e., is read to mean “including the specified examples and excluding other examples not listed.”
Although we can massage the drafting if need be, the difficult question remains: In a general convention, is it appropriate to use the same conception of “ship” for all purposes? Consider the issue of whether to exclude temporarily fixed platforms to illustrate the possibility that the definition should vary depending on the purposes for construing the term. It may be nonsense to consider fixed platforms as vessels if there is a concern with a rule like UNCLOS Article 111 on the right of hot pursuit, which contemplates a vehicle capable of self-propulsion. Yet with respect to other legal rules, e.g., rules related to the duty to rescue or to serious marine pollution, the case for a restrictive definition is not compelling. For example, the MARPOL Convention definition of “ship” is