Sayid is Sayid by OJ

I think that when Jacob died, the potency of the water diminished. We see the guy cut his hand and it doesn't immediately heal after he puts it in the water. They go ahead and dunk Sayid and, not surprisingly, he doesn't recover right after they release him.

But he does recover, it just takes longer than they are used to. Some of Jacob's power has diminished now that he has lost his physical form. Some say Sayid died, and now must be different because he came back to life. Well, the Others meant to kill him any way! We see him writhing as they hold him under the water until he goes limp while they wait for the sand timer to finish. Holding a mortally wounded person underwater would drown anyone.

So the only surprise is that he didnt come back to life sooner, in my opinion. This just means that Jacob's (or whatever force is powering Jacob and the water) powers are losing some of their potency, but in the end, the desired effect, Sayid's resurrection, still happened.