"God shut the door" means that God sealed their fate....safety from the flood...
Verily, verily, I say unto you, He that heareth my word, and believeth on him that sent me, hath everlasting life, and shall not come into condemnation; but is passed from death unto life.
What is your definition of "everlasting life"....what does "shall not come into condemnation;" mean?
What does "passed from death unto life" mean??
God did promise Noah, in his obedience, that he would deliver them from death by the flood.(In a similar way, Moses and the Israelites were delivered from the flood at the parting of the Red Sea. And yet all of that generation died except Joshua in the desert.) So what does that show us?
Noah and those members of his family, likewise died. And to extend that into the spiritual realm of Christ is a step to far, to say that one is permanently saved. It shows quite the opposite.
So just as in real life, if one walks in front of an oncoming car, or jumps off a high cliff, one may survive, likewise it is true of the Christian who does similarly(cause their death by sin in the spirit) with their faith, but there is no guarantee by God that His Judgment will not end in spiritual death, for those who abuse, or refuse the Christian way of life, after once accepting Christ as Lord.
Such a statement that he that hearth and believeth on him who sent me hath everlasting life, is just a part of the reality. We know that the demons and devil hear and believe whom Jesus is, does this mean that they have everlasting life?
It is when one hears and believes that begins the process of realizing one's hope, faith, and love are in Jesus Christ. So to "HEAR" means especially, while we are living that we have hope and faith in Jesus Christ. And while we are living, we do as Jesus did, and that is love God, one another, and take up our cross.
If one passes from death to eternal life, then why would not God reverse this process if one did not pursue the course of eternal life, but choose death by sinning, after someone is born again?(God does not override one's will before or after accepting Jesus as Lord.) But God's Mercy exceeds His need for Justice in the case of those who accept Christ. And it is there we have our confidence in the hope of eternal life with Him.