这些海浪在海上看起来不是很明显，因为它们的波长很长。

The waves are not noticeable out at sea because of their long wave length.

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反对者们还说，海堤阻挡了人们的视线，使人们不能观察海浪的变化，削弱了人们对海的了解。

Moreover, by literally cutting residents' visibility of the ocean, the seawalls reduce their ability to understand the sea by observing wave patterns, critics say.

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海啸可能达到的波高向来很难估计-海浪可能根本无法到达，或者可高达超出海平面10米。

It has been difficult to estimate the possible wave heights of any tsunami - the waves may not arrive at all or could be as high as 10 metres above normal sea level.

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