深海不见低情深不见心
[shēn hăi bù jiàn dī qíng shēn bù jiàn xīn]
In unfathomable depth of the sea as well as deep emotion there's no bottom limit means that deep affection cannot always be easily perceived just from surface appearance but runs deeply below it like an ocean. Just as you can't know what creatures are deep in the sea without diving deeper, so too does this phrase imply a hidden, deep love that isn't immediately visible.