shark in the water

Translations
опасный человек или ситуация
There are many sharks in the water in this business, so be careful.
В этом бизнесе много опасных людей, так что будь осторожен.
Definitions
A phrase used to describe a potential threat or danger that is present but not always immediately visible; it can refer to an actual shark in water or metaphorically to a person or situation that poses a risk.