That you can never see the sea as it's all mud.
Errrm, yes there are mud flats and with the second highest tidal range in the world, you're not going to be able to paddle in the sea unless you bother to check the tide times and plan your visit properly 
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At some points of the year, the sea actually covers the beach during high tide. I'm sure some people missed the moon and the sea bit at school. Or maybe they just like to moan.