。
The ship sank because of the storm.
Literal
Storm [because-of-ために] that ship [topic-は] sank.
沈む ('to sink') is an intransitive verb — the ship sinks by itself, no agent needed. Contrast with the transitive 沈める ('to sink [something]'), where someone actively sinks a target. Japanese systematically distinguishes these intransitive/transitive pairs and this one is a common study point.