immersion

(noun) sinking until covered completely with water. Synonyms: submergence, submerging, submersion.

(noun) (astronomy) the disappearance of a celestial body prior to an eclipse. Synonyms: ingress.

(noun) complete attention; intense mental effort. Synonyms: concentration, engrossment, absorption.

(noun) a form of baptism in which part or all of a person's body is submerged.

(noun) the act of wetting something by submerging it. Synonyms: submersion, ducking, dousing.