If water baptism was absolutely required for salvation, then God would not make so many statements in which He promises eternal salvation to those who simply BELIEVE
Just like they didn't have to say "you must hear the word, believe, have faith, accept Jesus...." yada yada....
'He who believes will be saved.....' all the rest is assumed... because it is all necessary. It's not necessary to spell it out every time salvation is discussed.
You keep saying that since it was NOT mentioned in a couple of instances, then it's not necessary. I can show you scriptures that say nothing of believing, or having faith, or even hearing for salvation. It does not follow that those things are not necessary, they simply were not mentioned, because they were assumed.
You cannot pick one or two verses and base your whole belief system on them. You have to read all of the scriptures pertaining to salvation.... even if it is stated in only ONE instance, it should be assumed it is part of EVERY instance.