Dazzle camouflage was effective at confusing observers on the surface; however, submariners were rarely fooled, as they tended to find ships' courses and speeds by looking at the masts and funnels, which dazzle camouflage did little to hide. The Royal Navy carried out an investigation into the utility of dazzle camouflage in 1918, which determined that "no definite case on material grounds can be made out for any benefit in this respect from this form of camouflage". However, as it was cheap to apply, and was good for the morale of merchant sailors, the committee recommended that it be continued. For more information on this topic, see this answer I've previously written.

One minor addition that might be of some use. The US Navy experimented with a false bow wave on some ships in 1941. An evaluation of this feature (Enclosure A, P.2, Sections B I. and B II.), which was sometimes added to Dazzle schemes, stated "Regardless of lighting, most observers base speed estimate on the wake."

This is probably not as true for submarines, with their lower observation point, but is worth adding.