A beautiful shell on the smooth surface of the seaA beautiful shell on the smooth surface of the sea
We are going to travel around the world on a cruise linerWe are going to travel around the world on a cruise liner
The sea foam of the blue sea rolls onto the sandy shoreThe sea foam of the blue sea rolls onto the sandy shore
Часть океана — большое водное пространство с горько-солёной водой. Большое количество чего-н. ( высок. ).