This is the 17905th most frequent Russian word.
утонувшего
"Uтонувшего" means "of a drowned person" or "drowned" in English.
Here, "утонувшего" (genitive singular masculine) is used as an adjective describing "корабля" (ship), indicating it has sunk.
Он рассказал историю утонувшего корабля.
He told the story of the sunken ship.
In this context, "утонувшего" (accusative singular masculine) is used as an adjective to describe "котёнка" (kitten), indicating it had drowned.
Мы нашли утонувшего котёнка возле реки.
We found the drowned kitten near the river.
Here, "утонувшего" (genitive singular masculine) is used as an adjective related to "пассажира" (passenger), conveying that the passenger had drowned.