Conventional wisdom would tell you that any ship going unnoticed by the enemy, especially an enemy submarine in World Wars I and II, would be the best-case scenario. But the Navy's "Dazzle" camouflage was clearly anything but conventional. The ships feature a paint job that looks more Picasso than Portsmouth, but anything that could save a ship's crew and cargo was worth a try.
Try not to have a seizure.
The "camouflage" used on each of the Navy's "Dazzle Ships" was unique to the ship, and its purposes were many. First, it prevented the enemy from identifying the ship, its class, its cargo, or even what kind of ship it was. It also made determining the ship's course and speed difficult. If an enemy u-boat can't determine the ship's course, then it will also have difficulty moving to the best firing position, course and speed being necessary factors in targeting a ship with a torpedo.
Dazzle camouflage also made rangefinding for artillery and other ship-borne weapons very difficult, as it disguised many features used by captains and gunners for determining the range of the enemy target. One enemy captain called it the best camouflage he'd ever seen:
"Since it was impossible to paint a ship so she could not be seen by a submarine, the extreme opposite was the answer – in other words, to paint her not for low visibility, but in such a way as to break up her form and thus confuse a submarine officer as to the course on which she is heading."
A U-boat commander's periscope view of a merchant ship in dazzle camouflage and the same ship uncamouflaged.
By the end of World War I, the United States and the United Kingdom had thousands of ships in service wearing dazzle paint. While there is little statistical data available that the dazzle patterns actually worked, the U.S. and Royal Navy both tested it extensively on small boat operation before implementing it, and anecdotal evidence suggests it was effective, as does a 1918 song by Gordon Frederic Norton, called "A Convoy Safely By."
Captain Schmidt at the periscope
You need not fall and faint
For it's not the vision of drug or dope,
But only the dazzle-paint.
And you're done, you're done, my pretty Hun.
You're done in the big blue eye,
By painter-men with a sense of fun,
And their work has just gone by.