I saw previews for this made-for-TV movie in Montreal in the 80's and as an armchair sailor was intrigued. I watched it for the swashbuckling and fell in love with it for the plot. The movie was low budget but the plot and dialog were brilliant. I was compelled to read the book, which of course was even better.
Later I spent 8 years cruising the Bahamas and Caribbean, earned my commercial captain's license, and ran charter boats for a living, but this plot still stays with me, and I recount it to people all the time as probably the most captivating sailing yarns I know.
Most maritime survival adventures focus on the strength of human will and cleverness over the elements and that's pretty much it. The better ones combine salty tales with intrigue and fascinating character development. The poorer ones simply recount a the events of a struggle against the sea. Some I have read are hopelessly boring in spite of being true stories of a life-and-death struggle.
This story has the salty intrigue in spades, but it really serves as a brilliant setting for a lengthy and gripping dialog on the paradox of faith. If you're a sailor you'll love it. If you're a theologian, or intrigued by the phenomenon of religion and faith, you'll love it.
It reminds me a bit of C. S. Lewis' "Out Of The Silent Planet", a much more masterly allegory of two characters pitted against each other on the subject of blind faith vs. pragmatic realism in a setting where lives depend on the result. "Lost!" is much simpler, but the dialogs are no less thought provoking and poignant.
In spite of the lackluster title, the writing is simple and very well thought out. The characters and dialogs are believable. In my mind it's a hidden gem because nobody I have ever known has ever heard of it, and yet it was a very formative story for me while I dreamed of cruising. I highly recommend it.