Made up mostly of limestone formed from the skeletal remains of sea creatures, the submerged regions of the tidal flats are carved by channels where water flows between land.
这些群岛主要是由海洋生物残骸形成的石灰岩构成，潮汐滩的水下部分被流动的水分割成河道。
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A microscopic skeletal plate made of calcite that protects certain Marine phytoplankton and which, in a fossilized state, forms chalk and limestone deposits.