Answer:
The trench is too deep where sunlight cannot reach it.
Step-by-step explanation:
Water gets colder with depth because cold, salty ocean water sinks to the bottom of the ocean basins below the less dense warmer water near the surface. The sun's energy only reaches the surface of the ocean, and the deeper you get—from about 50-60 feet and onward—there's what is known as a “cold pool.” The sun can't penetrate the cold pool, so winter weather water remains in the deep ocean. You might expect the waters of the Mariana Trench to be frigid since no sunlight can reach it. And you'd be right. The water there tends to range between 34 to 39 degrees Fahrenheit. But what's surprising is how hot the water can get, too.