It’s about drugs. All Sixties songs were about drugs.
Happy now?
I notice that the Wikipedia page on The John B Sails (the original song on which the Beach Boys version was ultimately based) makes no reference to a captain John Bethel or his ship, the solution scottburlin brought up recently. The song is traced no farther back than 1916, with no suggestion of when the Jphn B – if it actually existed – actually sailed. Some people suggest as far back as the 17th century, when a captain John Bethel evidently was around. That “everyone on Nassau” knows the origin , unfortunately, isn’t sufficient pedigree. In the absence of documentary proof, it’s like hearsay. For all we know, the song might date no further back than 1916, and be wholly fictional.
Here’s another, weirder theory:
I think it’s extremely unlikely that this variant originated with Brian Wilson. “This is the worst trip I ever was on” is how the line appears in the book of folk songs I got when I was first learning guitar. Although the book was published in 1967 and so postdates the Beach Boys recording, the lyrics have enough small differences that they clearly are not copied from that version, and the book otherwise shows no rock influence–the version of “House of the Rising Sun,” for example, has very little in common with the Animals’ version.
Well, how good technically are the other lyrics? In other words, do they rhyme? Do they scan? Do they use obscure words? Could Burdon and The Animals have sung them intelligibly?
Like others have said I’ve always thought it was pretty straight forward, the opening scene in a coming of age tale. The “grandfather and me” line frames the story. It’s sung from the point of view of a young’n from a sea faring family on his first real voyage. All this crazy sh#t happening. For him it’s wild, scandalous and undesirable. For grandpa, it’s business as usual.
Occam’s Razor, you know. 
“The John B. Sails” is a Bahamian folk song from Nassau. A transcription by Richard Le Gallienne was published in 1916, and a version was included in Carl Sandburg’s The American Songbag in 1927. Since the early 1950s there have been many recordings; variant titles include “I Want to Go Home”, “Wreck of the John B”, and “Sloop John B”.
The song was transcribed by Richard Le Gallienne, with five verses and the chorus published in his article “Coral Islands and Mangrove-Trees” in the December 1916 issue of Harper’s Monthly Magazine (pp. 81–90). The first two verses and chorus were also published in Chapter IV of Gallienne’s 1917 novel Pieces of Eight.
As others have noted, it’s probably pretty literal.
All I know is, my grandfather would’ve been bursting with pride had I gotten liquored up and gotten into a drunken brawl. I think my more cerebral nature was a disappointment to him. 
Too bad he didn’t live another 10 years or so to see me as a Marine.
Your grandfather may have read *Outlines of History, * particularly Page 1005 (of the 1921 edition, at least), where Wells quoted Friedrich Nietzsche on war.
This is in response to and ScottBurlin and Calmeacham’s posts:
The folk song John B Sails later known as Sloop John B made famous by the Beach Boys has truly been a Bahamian folk song for at least 100 years. Scott must have stayed at our family home; Tamarind in Governor’s Harbour Eleuthera. Our parents bought Tamarind over 40 years ago and my brother and I still own and run it. Tamarind has had only 4 owners in it’s 140+ years of existence. The original builder and owner was the Sea Captain John B (Bethel) who built Tamarind in the mid to late 1870’s as a wedding present for his wife during the time that Cupids Cay (off of Governors Harbour) was the original capitol of the Bahamas. At that time there was no bridge connecting the mainland to the Cay just sailing vessels beam to beam bridging the divide. John Bethel built his Sloop John B in our back yard and ran it on skids down into the harbor. John B was outlived by his wife who remained at Tamarind until she died in I believe the late 1920s or early 1930. Our maid who was with us for many decades clearly remember the Widow Bethel who lived at the Sea Captain’s home.
Hope this helps.
This is in response to and ScottBurlin and Calmeacham’s posts:
The folk song John B Sails later known as Sloop John B made famous by the Beach Boys has truly been a Bahamian folk song for at least 100 years. Scott must have stayed at our family home; Tamarind in Governor’s Harbour Eleuthera. Our parents bought Tamarind over 40 years ago and my brother and I still own and run it. Tamarind has had only 4 owners in it’s 140+ years of existence. The original builder and owner was the Sea Captain John B (Bethel) who built Tamarind in the mid to late 1870’s as a wedding present for his wife during the time that Cupids Cay (off of Governors Harbour) was the original capitol of the Bahamas. At that time there was no bridge connecting the mainland to the Cay just sailing vessels beam to beam bridging the divide. John Bethel built his Sloop John B in our back yard and ran it on skids down into the harbor. John B was outlived by his wife who remained at Tamarind until she died in I believe the late 1920s or early 1930. Our maid who was with us for many decades clearly remember the Widow Bethel who lived at the Sea Captain’s home.
Hope this helps.
This thing has been revived about ten times. I seem to have missed it almost every time. But I am pleased as I can be to see that Ukulele Ike was being a smartass as long ago as 2002 (post8). Keep up the good work, King of the Dopers.
The apparent fact that there was a real John B who built a real boat, does not in any way show (or even hint) that the song is based on real events. It could very easily be a fantasy song based on nothing, using the names of real people and places just for fun.