沉船残骸位于海床之上。

The shipwreck lies on the ___bed of the ocean.

有时能在干涸的河床中发现化石。

Fossils can sometimes be found in the ___bed of a dried-up river.

潜水员探索了地中海多岩石的海床。

Divers explored the rocky ___bed of the Mediterranean Sea.