I wouldn't sail this ship if I were you
1. Hopkin’s Worm (note: this is a misclassification as Hopkin’s Worm is now thought to be an unusual crustacean). A rare example of a bellybutton-based parasite. The young of this creature resemble short, dark threads and often infest cotton-based clothing. Once it has made its way to the bellybutton, Hopkin’s Worm loses the ability to crawl and becomes entirely reliant on its host, living off the lint it gleans from the host’s clothing. Hopkin’s Worm’s hosts therefore often seem to have unusually clean bellybuttons. Interestingly, Hopkin’s Worm has no excretory facilities, instead becoming significantly larger throughout its lifespan; however, this growth is usually mistaken for middle-aged spread by the host.
2. Annifaners. These barely-visible mites live in the human ear, where they live on, in and protected by earwax. Their presence is almost undetectable by the host; however, annifaner mating is known to make a quiet rustling noise, a little like the sound of the sea far off. Since they primarily mate at night, annifaner hosts are more likely than most humans to dream of the ocean.
3. The Hammerian Hat. There is in fact only one known Hammerian Hat in existence, and it seems likely that it is the last of its kind. The Hammerian Hat in its dormant form resembles a simple cotton skullcap. If worn for any length of time (particularly if slept in) it will attempt to fuse to its host, consuming their hair and in turn growing its own pseudo-hair, as well as a set of roots with which it connects to the host’s circulatory system. The host merely notices that the hat has disappeared and that they are having a very bad hair day. The only known specimen disappeared from a research lab in the early 1920s, so it may be that the Hammerian Hat is now entirely extinct.
4. Gorlocks. These small parasitic shadows do not eat, excrete or reproduce; it is thought, in fact, that the Gorlock population on Earth has remained stable since at least the time of the dinosaurs. Their original origin is not known. They attach themselves to host entities purely to get protection from direct sunlight, which they dislike. As they overlap the host’s original shadow, Gorlocks are almost undetectable unless the host is in bright non-directional light, at which point they will attempt to hide. Gorlocks usually attach to trees but can occasionally be found on humans.
5. The Worcestershire Farter. This creature typically masquerades as someone known to the host, appearing at the door as if for a social visit with a sign requesting food and drink (typically offered with the excuse that the Farter has a very sore throat and cannot speak). Unbeknownst to the host, the Worcestershire Farter is in fact a highly-developed colony of single-celled organisms which is has taken on, chameleon-like, the appearance of a previous host. After it has been fed, the organisms produce prodigious amounts of gas through all available orifices; typically, by this point, the bodily facsimile is deteriorating and it may develop a few new orifices as well. During this phase, the Farter begins to take on the characteristics of the current host. By the time it has ejected itself from the host’s home (usually before the arrival of any ambulances) it has fully adopted the appearance of the host and typically stolen their phone or address book, ready to move on to the next host. The Worcestershire Farter can be deterred on initial presentation by asking it to remove its hat, since its clothes are part of it rather than separate garments.
6. Scumble-oybles. Small parasitic words which, once heard, stick in the back of the brain such that the host is never quite sure if they are a real word with a dictionary definition or merely a random collection of letters. Central to the Scumble-oyble survival strategy is the impression that, were they a real word, they would be such an usual and commonplace word that the host could feel justifiable embarrassment about looking them up.