If the ground or sea is treacherous, it is extremely dangerous, especially because of bad weather conditions. (Cambridge Dictionary)
Likely to betray trust: Unreliable. (Merriam – Webster)
Providing insecure footing or support. (Merriam – Webster)
Marked by hidden dangers, hazards, or perils. (Merriam – Webster)
Guilty of or involving betrayal or deception. (Oxford Dictionaries)
If you describe someone as treacherous, you mean that they are likely to betray you and cannot be trusted. (Collins Dictionary)
If you say that something is treacherous, you mean that it is very dangerous and unpredictable.
The Human Heart Is Treacherous.
The Treacherous and Productive Seas of Southern Africa.