boat和ship分别是in the sea 还是on the sea at

boat和ship分别是in the sea 还是on the sea at in the sea还是on the sea On the sea 和in the sea sea 和at the sea fly in the sea还是fly on the sea? travel in the sea 还是 travel on the sea.. 辨析at sea / on the sea in the sea on the sea,at sea有什么区别 in the sea ,on the sea ,at sea 有什么区别, in the sea 和at sea 有什么异同? in the sea 和on the lake by sea,at sea,on the sea有什么区别?分别造句,