sinking

uppoaminen

heikkeneminen, laskeutuminen

vajoaminen (present participle of)
The act or process of sinking.

I witnessed the sinking of my ship from the shore.

We must endeavour to realize a succession of gradual sinkings or depressions into deep water, alternating with gradual emergings into shallows, and eventually a gradual continued lifting of the whole district(..)