immersion has 9 distinct synonyms spread across 4 of its 5 senses. Each sense below keeps its own list, because a synonym belongs to a meaning and not to a word: swapping one sense's substitute into another sense's sentence is how a thesaurus makes writing worse. Its one recorded opposite is emersion.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
sinking until covered completely with water
(astronomy) the disappearance of a celestial body prior to an eclipse
complete attention; intense mental effort
a form of baptism in which part or all of a person's body is submerged
Synonyms, antonyms and the broader and narrower relations for immersion come from Princeton University’s WordNet. Full sources and licences.