你若深似海我便久沉溺
[nĭ ruò shēn sì hăi wŏ biàn jiŭ chén nì]
If you are as deep as the sea, then I shall be engrossed in love with you for a long time. This nickname expresses strong, undying affection towards another being, highlighting the depth and duration of emotions similar to endless oceanic abysses.