Just because Its in the jutsulist doesn't mean everybody can use it the same way. Temari uses wind jutsu with her fan, do all of us carry around fans to use wind jutsu? No, we use hand signs and such to create them. Same thing here it's just slightly different. Nidaime was said to be able to use some of the most powerful water jutsu out of thin air, he was also said to be the strongest water user ever. Even if it is only a 1 second difference(which it probably is a bit more but meh) at his current speed that's all the time he needs.The jutsu works the same for everyone that uses since its on the jutsulist. so even though it would happen faster if I was 2nd Hokage, im more then sure the 1 second it takes for this jutsu to have enough water to kill him would be enough. it takes less then a second for someone to clasp their hands, try it.
then the next second enough water would be there so that it would kill him..
Anyway I'm not here to argue just stating my opinion. Get an RP mod to check it =/