sea
1.说“…海”该有the，如the Mediterranean Sea（地中海）和the Caspian Sea（里海）。
2.下面每句里用the seas：
- They have gone over the seas back to England.
- The story is told by an aged warrior of the seas.
3.at sea是“在海上”或“在海里”，往往含有“离海岸很远”的意思。例如：He spent years at sea. 和He was buried at sea. at the sea＝at sea。by sea是“由海路、乘海船”。例如：They came by sea. by the sea是“在海岸上”。例如：They live by~the sea. in the sea是“在海里”，不是“在海面上”。on the sea有时是“在海面的船上”，有时是“在海岸上”。
4.go to sea通常是“开始做水手”，有时是“开航”。go to the sea是“到海滨去（度假）”。go into the sea是“到海里去”。run off to sea是“逃去做水手”。例如：He ran off to sea when he was young. put out to sea是“开航”。例如：Next morning we put out to sea.
