I probably found it a few years ago, while reading an article about funny Amazon reviews.
Yes! Captain Trimmer was a Master Mariner and a harbor pilot. The book was sincere; apparently the Captain had seen many pleasure-boaters doing stupid things out there and failing to understand the physics involved in encounters with Huge Ships:
https://en.wikipedia.org/wiki/How_to_Avoid_Huge_Ships
Then I really hope he hasn’t read the reviews. People making light of something he find serious could be insulting. Either that or I hope he has a fantastic sense of humor.
I might have to read “Greek Rural Postmen and Their Cancellation Numbers” next, LOL!