The submarine will most likely find data that shows the highest pressure data and the lowest temperature data (unless of course it's near a hydrothermal vent). This is because due to the depth there's a lot more water above it putting a lot of pressure on the sub, and very little sunlight to heat up the water.
Answer:
I think its organic material from plants and animals
Explanation
Edge 2020
<span>3) Oceans
The oceans are a massive carbon sink, and part of the positive reinforcement of the greenhouse gas cycle is that, as the oceans become warmer, then tend to release more carbon dioxide dissolved in the water which in turn drives temperatures warmer.</span>