海是一座无墙的城心是一个无底的洞
[hăi shì yī zuò wú qiáng de chéng xīn shì yī gè wú dĭ de dòng]
The literal translation reads as 'the sea is a wall-less city; the heart is a bottomless pit.' It suggests the vast openness and mystery of the sea akin to how boundlessly extensive our mind or emotions can be, both profound and unpredictable.