Per Lord Blackburn in Steel et Al. v The State Line Steamship Company (1877-78) L.R. 3 App. Cas. 72 at p. 90-91:
If, for example, this port was left unfastened, so that when any ordinary weather came on, and the sea washed as high as the port, it would be sure to give way and the water come in, unless something more was done – if in the inside the wheat had been piled up so high against it and covered it, so that no one would ever see whether it had been so left or not, and so that if it had been found out or thought of, it would have required a great deal of time and trouble (time above all) to remove the cargo to get at it and fasten it--if that was found to be the case, , I can hardly imagine any jury finding anything else than that a ship which sailed in that state did not sail in a fit state to encounter such perils of the sea as are reasonably to be expected in crossing the Atlantic. I think, on the other hand, if this port had been, , open, and when they were sailing out under the lee of the shore remaining open, but quite capable of being shut at a moment’s notice as soon as the sea became in the least degree rough, and in case a regular storm came on capable of being closed with a dead light – in such a case as that no one could, with any prospect of success, ask any reasonable people, whether they were a jury or Judges, to say that that made the vessel unfit to encounter the perils of the voyage, because that thing could be set right in a few minutes, and there is always some warning before a storm comes on, so that they would have plenty of time to put it all right, and it would have been put right. If they did not put it right after such a warning, that would be negligence on the part of the crew, and not unseaworthiness of the ship. But between these two extremes, which seem to me to be self-evident cases as to what they would be, there may be a great deal of difficulty in ascertaining how it was here.
In Papera Traders Co. Ltd. v Hyundai Merchant Marine Co. Ltd (The Eurasian Dream)  EWHC 118 (Commercial) Cresswell J said at para 129:
(3) Incompetence is to be distinguished from negligence and may derive from:
(a) an inherent lack of ability.
(b) a lack of adequate training or instruction: e.g. lack of adequate fire- fighting training.
(c) a lack of knowledge about a particular vessel and/or its systems: The Farrandoc  2 Lloyd’s Rep. 276.
(d) a disinclination to perform the job properly:
In considering efficiency, the matters to be considered, in my view, are not limited to a disabling want of skill and a disabling want of knowledge. A man may be well qualified and hold the highest grade in certificates of competency and yet have a disabling lack of will and inclination to use his skill and knowledge so that they are well nigh useless to him. Such a man may be unable efficiently to use the skill and knowledge which he has through drunken habits or through ill-health. Mr MacCrindle has submitted that a lack of application in the use of skill and knowledge is not within the ambit of "competence", though in certain cases he would be prepared to accede that drunkenness and physical unfitness might be.
This is a matter to which I have given considerable thought and I can see no real difference between those two, that is, drunkenness or physical unfitness on the one hand and a disabling lack of will to use the skill and knowledge on the other. The reason why I can see no distinction is that the result is the same, or may be.
The Makedonia  1 Lloyd’s Rep. 316 at 335 per Hewson J.
(e) physical or mental disability or incapacity (e.g. drunkenness, illness): Moore v Lunn (1923) 15 Ll.L.Rep. 155; Rio Tinto v Seed Shipping (1926) 24 Ll.L.Rep. 316.