潜函 is read as せんかん (senkan) and means caisson.
せんかん
senkan
せんかんびょう
caisson disease
せんざい
potentiality
せんすいかん
submarine
ひそむ
to lurk
くぐる
to dive (into or under the water)
せんぷく
concealment
せんにゅう
infiltration
せんすい
diving
せんこう
underwater navigation
せんざいいしき
subconsciousness
submarine voyage
もぐりこむ
to sneak into