It's impossible to conclusively say whether dazzle worked or not, due to the large number of confounding variables. One study, which I unfortunately forget where I read it, came to the tentative conclusion that it was probably mostly a wash. Yes, dazzle helped somewhat and there was as a result a slightly lower percentage of successful attacks (that is, more torpedoes that missed their target), but OTOH due to being easier to spot in the first place the dazzle painted ships also invited more attacks.