波罗的海

bō luó dì hǎi shì běi hǎi de yán shēn hǎi yù

波罗的海是北海的延伸海域。

The Baltic Sea is a continuation of the North Sea.

tā men jǐn píng yī gè luó pán de zhǐ yǐn shǐ guò le bō luó dì hǎi hé běi hǎi

他们仅凭一个罗盘的指引驶过了波罗的海和北海。

They sailed across the Baltic and North Seas with only a compass to guide them.