The only people noted to have been immersed prior to John the Baptist were the antediluvians, and on another thread it was noted that the general consensus around here is that those people were NOT saved (although I hold out hope that many of them repented as the water approached nose level).
It should also be noted that Moses' biggest miracle was in preventing the "baptism" of the Israelites as they crossed the red sea.
So if Baptism is a requirement for salvation, then most, if not all, of the old testament patriarchs are out of luck.
But wait, isn't there a sect that does baptism for the dead?
??? Find a Jew, and ask them what a "mikve" is.
Baptism is a Greek name for a Jewish ritual, prescribed over and over again in the Law.
I share your desire to see some saved, but the Ark represented salvation.
Only those who were in it were save since they believed God.
Enoch (a type of the church) was 'raptured' out before the flood.
All those who went through the flood had time to repent but refused.
It is more likely that they had become so hardened that they were unable to repent even with the water coming over them.
You are trying to place items of the New Covenant on those who were under the Old Covenant. That is not Biblical. The Old Testament patriarchs did not require baptism because they lived under a Law which required many sacrifices. The final sacrifice was made when Christ died and rose again.