Our knowledge of the ocean a hundred years ago was confined to the two-dimensional shape of the sea surface and the hazards of navigation presented by the irregularities in depth of the shallow water close to the land.
这是我会翻译给学生看的：
我们一百年前关于海洋的知识局限于二维度的海面形状，以及靠近陆地的浅海的深度之不规则所造成的对航海的危害。
这是新概念教材会翻译给学生看的，大家仔细看看，似乎意思也偏了点呢。作为大概意思的版本还可以。
100年前，我们只知道海洋是二维平面形的，以及靠近陆地浅水区的深浅不一能给航行带来危险。
Our knowledge of the ocean a hundred years ago
was confined to
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the two-dimensional shape of the sea surface
and
the hazards of navigation {presented - by the irregularities in depth of - the shallow water close to the land}.
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