久溺深海冷不冷久溺深海就不冷
[jiŭ nì shēn hăi lĕng bù lĕng jiŭ nì shēn hăi jiù bù lĕng]
The phrase can be understood as 'If you stay immersed in the deep sea for long, does it feel cold? When you have stayed long enough, it no longer feels so.' It metaphorically conveys that one gets used to the situation even if it seems harsh at first.