Your text is mostly clear, but here are a few grammatical and stylistic suggestions for improvement:
Some might say that the megalodon is still alive and living in the deep ocean, but could the megalodon survive the pressure in the deep? The megalodon would not be able to survive in the deep ocean for many reasons. One is the availability of food. The deep sea is so dark that it would be nearly impossible to see because of how dark it is. Smaller animals are adapted to survive long periods without food and can eat scraps from the upper areas of the sea. The megalodon would need tons of food to survive due to its size. Another reason the megalodon could not survive in the deep ocean is because of the pressure. The high pressure from the depths would crush the megalodon since it is not adapted to live under such high pressure.
Changes made:
- Removed "that" for improved flow in the first sentence.
- Changed "long times" to "long periods" for clarity.
- Added "of" after "tons" to make "tons of food."
- Changed "the deep" to "the depths" for clarity in the last sentence.
Feel free to let me know if you have any other questions!