Navigating in these non-tidal, archipelic waters calls for first class communication and coordination between the navigator at the chart table below and the lookouts and helmsman on deck. With an infinite multitude of islands, and an equal number of safe and definitely unsafe passages between them, it is vital that there is a clear and concise understanding between all with regard to what you can see and what you are looking for.

Snurgly: a small island, properly removed from other nearby land, consisting entirely of well-rounded rock, and devoid of vegetation. 

Snurglette: as above, but too small to warrant classification as a Snurgly.

Nasty Bastard: a Snurgly or Snurglette that does not break surface and therefore could easily not be detected before you hit it.  Must have less coverage over it than the depth of your keel. Possible aid to detection: may have waterfowl feeding in its vicinity. Terminology may be abbreviated to 'NB' should one be with polite company, not attuned to nautical language.

We'll let you know if we have an unwanted close encounter with any of the above....