Usually, the smoke screen had to be laid by DDs traveling parallel to the overall fleet direction and slightly ahead of it, otherwise the smoke would only conceal the back halves of the ships laying it. If the smoke is relatively cool and hangs low to the water, then aircraft above will have no trouble spotting or dive-bombing from above, although it MIGHT make the approach runs of torpedo bombers a bit more convoluted. If the smoke is warm, and rises to form a hazy overhead blanket, then it won't hug the water, and the torpedo bombers will typically fly UNDER the heavier concentrations, while other surface ships will be less affected by it as well, and it STILL won't hide the ships from aircraft overhead, because they'll see over it to the ships within the formation.
Note that it still won't hide the ships completely from ANY attackers except behind the densest pockets, but it will make shell-splashes difficult to judge, and may lead to confusion as to whether that's a capital ship and a couple of escorts, or two capital ships and an escort or two. It will also make it very hard to determine if that "other" ship is partly in front of it and blocking it, or partly behind it. German "fracture" camo was designed to maximize the confusion about where the bow and stern began and ended, and made it difficult to tell whether you were seeing one ship or two, or even three. It didn't hide the actual presence of the ship(s).
