I had never heard that, but perhaps it explains why submarines are called boats in general.
Some submarines can of course carry other smaller vessels, and perhaps even a torpedo might be considered a "vessel", depending on how THAT is defined.
I don't know if there's a universally agreed-upon definition of
boat compared to
ship. But the submarines of modern navies are certainly ships.
The two-man midget subs that were part of the Pearl Harbor attack? I think they should properly be considered boats.
Speaking of those midget subs, one of them is involved with an interesting story.
In 1918,
Wickes-class destroyer
USS Ward was built in a record 17-1/2 days at Mare Island Navy Yard, CA. She was laid down on 15 May and launched on 1 June. She was commissioned on 24 July. She was transferred to the Atlantic just about the time that the Great War ended. She was part of the surface support of the trans-Atlantic flight of the U.S. Navy's NC flying boats in May 1919. She returned to the Pacific a few months later and was decommissioned on 21 July 1921.
Here's a semi-well-known picture of "Destroyer No. 139" under construction.
[img width=397.983 height=500]https://inchhighguy.files.wordpress.com/2019/01/ward01.jpg[/img]
The outbreak of WWII in Sep 39 brought
Ward back into service. She was recommissioned on 15 Jan 41 and sent to Pearl Harbor soon thereafter. She operated on local patrols over the course of the year. On 5 Dec 41 she got a new skipper, Lt. Cdr. William Outerbridge. It was his first command.
Two days later, before dawn, Ward was patrolling off the entrance to Pearl Harbor. At 0357,
Ward got a visual signal from minesweeper USS
Condor (AMc-14) that a periscope had been spotted.
Ward began searching for that periscope. At 0637, she spotted what looked like a conning tower trailing cargo ship USS
Antares (AKS-3) heading toward the entrance to the harbor. Otterbridge gave the command to open fire, and at about 0645 she holed and sank the midget sub that that conning tower belonged to.
Ward thus drew first blood in the war between Japan and the U.S. She reported the sub engaged and sunk twice, at 0651 and 0653, but delays in seeking confirmation and reluctance to believe the report resulted in the message not being rapidly transmitted up the chain of command.
In 1942,
Ward, redesignated as APD-16, along with several other 4-stacker destroyers, was converted into a high-speed troop transport. She steamed to the South Pacific in early 1943. She served in the Solomons campaign, helped in the defense of the air attack on Tulagi, participated in the Cape Gloucester invasion, and participated in the assaults on Saidor, Nissan Island, Emirau, Aitape, Biak, Cape Sansapor, and Morotai. By Oct 44, she was operating in and around the Philippines. Per the Font of All Wisdom and Knowledge:
On 17 October 1944, she put troops ashore on Dinagat Island during the opening phase of the Leyte invasion. After spending the rest of October and November escorting ships to and from Leyte, in early December, Ward transported Army personnel during the landings at Ormoc Bay, Leyte. On the morning of 7 December, three years to the day after she fired the opening shot of the Pearl Harbor attack, she came under attack by several Japanese kamikazes while patrolling off the invasion area. One bomber hit her hull amidships, bringing her to a dead stop. When the resulting fires could not be controlled, Ward's crew was ordered to abandon ship, and she was sunk by gunfire from [USS] O'Brien [DD-725], whose commanding officer, William W. Outerbridge, had been in command of Ward during her action in Hawaii three years before.