some conditions that could make it difficult to live or survive in could be to hot or cold,no air,and water pressure when you get to deep into the oceans.
An extreame environment for a human would be somthing so inposable or to difficult to surviv in.
Technology help alot of people.(ex) there is a new robot called the ropot that can go to the very bottom of the see so scientist can see whats on the bottom and explore the oceans.