User blog comment:DancePowderer/Haki Problems/@comment-1940096-20110121164240/@comment-3242083-20110123131852

"Oda stated in the SBS that Devil Fruit users are susceptible to all types of water, not just seawater. He elaborated on this, saying that "moving" water, like rain or waves, does not weaken Devil Fruit users, while standing water does."

Ace wasn't drenched in water. Even if he was, it would have no effect (only standing water has an effect, doesn't matter if it is seawater or not.) People are so fixated on Jinbe disabling Morias zombies, while it is clearly stated that it was not the seawater,  but the SALT in the seawater that did the trick. It is a special weakness to Morias abilities, not all users.

And to why Jinbe just blocked: Well, Akainu tells him that he (Jinbe) exactly knows what he is capable of and that he stands absolutely no chance. Akainu proved that even if he is attacked by haki users (Vista, Marco) it means nothing to him. So yeah Dancepowderer, why didn't he make use of seawater there, if it is a way to hurt logias? It doesn't work. That is why Jinbe resorted to the only thing he could do: taking all direct hits to buy a few seconds for the others.

That is the conclusion. We could speculate on Ace's special weakness to water, we can make up a whole new scenario for their fight - but only haki is the confirmed way to hurt a logia.

Again, it is still a conclusion - but as with Laffittes devil fruit, it seems to be allowed.