According to Baidu Library, "charming and peaceful ocean" is a rhetorical device, which is usually used in poetry or literary works to describe the beauty and tranquility of the ocean in a certain state. This expression means that the ocean is very attractive and quiet at a certain moment or situation. Here, "charm" refers to the beauty and attraction of the ocean, while "tranquility" implies the calm state of the ocean surface.
This poetic depiction aims at arousing readers' admiration and awe of nature, leading readers to enter a state of mind beyond the world and feel the wonder and tranquility of nature.