The immigrants make the dangerous voyage there, packed like sardines in wooden fishing boats.
Literal
Immigrants [topic-は], there [to-へ], wooden fishing-boats [in-に] sardine-packed state [at-で], dangerous voyage [object-を] do [copula-のである].
すし詰め状態 'packed like sushi' — literally 'sushi-stuffed state,' the Japanese equivalent of 'packed like sardines.' 木の漁船 'wooden fishing boats.' のである is a formal explanatory ending. The sentence describes dangerous migration conditions.