Excuse me, isn't God Spirit that is ever-present everywhere and always? Isn't the whole world immersed in God's presence?
This is not to suggest a physical sensation or some type of emotional experience ..., but the regeneration of the human spirit is sometimes associated with other phenomenon in some believers coincident to that salvation
What does that have to do with being immersed?
Have you ever jumped into a pool of water such that you are completely immersed? The sensation of our thinking through faith in Christ with that immersion is somewhat akin the the sensation of being immersed in water. Not identical to it, but a similarity to communicate how the worldly and fleshly impacts upon our thinking no longer take priority as when we remain in fellowship with Him.
Off the top of my head there are 7 different types of baptism used in Scripture. The baptism of the Holy Spirit is the regeneration of the human spirit, the initial instant of our receiving eternal life.