“water and by water” and “the present heavens and earth are being reserved for fire”, what is the universal...?

The answer lays in the translation of terminology. Instead of the "Planet Earth" replace "World" with your individual "Body", which is made up of almost all water. The "Fire" being spoken of is the Spirit of the living God; for "I am an all consuming fire", and again "I shall baptize you with power and fire". The only universal end is not a collective end. It is, instead, a progressive end, as in, the old way of thinking will pass away and be forgotten. The destruction is of the evil or dark understanding within, from within our Souls/Minds which we were born into. The system of "Death" thought will pass away and "Life" thought will emerge, thus, creating a new Heaven and a new Earth within the individual who is being reborn into the Kingdom of Christ and His Mind. When we become as the mind of Christ then the ungodly is burnt up. Only then can the New Jerusalem come down out of Heaven (within you) and burn through the layers of flesh, as salt, roasting the flesh and turning it into Spirit flesh and immortality; like Jesus in the upper room, who could be touched and yet, walk through walls. If He could be touched then He was flesh, but He was not mortal flesh. Only He that is from above may return (be one with the Father). The only way to get there is to become like Him in Spirit, Soul, and Body, by and through the Blood, Spirit, and Grace of Jesus Christ and of the Father. Everything Jesus did was for this purpose or "End". God Bless