sea是可数名词吗

例句：

The waste was dumped in the sea .

废物倒入海中。

The wreck is lying at the bottom of the sea.

沉船躺在海底。

He looked down at the sea of smiling faces before him.

他看着眼前这笑脸的海洋。

The sea covers nearly three-fourths of the world's surface.

海洋几乎占地球表面的'四分之三。

The small craft was exposed to the danger of the open sea.

那只小船曾经历了在空旷的海洋里穿行的种种危险。