Submersion
Flood
Immersed in water. That sounds like submersion. Possibly like a flood, even.
しんすい
This is a jukugo word that uses the on'yomi readings of the kanji. You should be able to read this on your own.
気温が上がるのは素晴らしいことだけど、私達は雪解け水による浸水を心配しています。
It’s great that the temperature is rising, but we’re worried about a flood from the melting snow.