You don't need to overthink too much, AQ.
As Carsten relates, it's just an extra administrative step that, once known, you just comply with and work your way through the various requirements. I remember staying a couple of extra days in the capital of Vanawatu, waiting for our paperwork for New Caladonia.
Regarding unforeseen contingencies, there is a safe harbour provision. Let's say you were caught out in extremely bad weather
and deeked into the nearest safe harbour to anchor
- which happened to be a country for which you did not hold a visa.
It's all about dealing with that country's authorities as soon and as honestly as possible. While at anchor
, fly your Q-Flag. Try to raise someone on the radio
to ask where you would properly clear in (or just read the cruising guide that you'll probably have onboard).
Of course, Covid has complicated things to an extreme extent, but the treatment you would receive would vary by country and the actual customs/coast guard officer with whom you're dealing, but if you default to honesty and civility - and patience
, it will take you far.
is a good resource (it gets recommended on this Forum a lot) but I can't vouchsafe, as I've never used it.
My MO is to talk to fellow cruisers and ask questions of them as I go along. Our sailing community is a great resource (and not just on this Forum).