As you go deeper into the ocean the temperature increases or decreases or stays the same

The temperature Decreases. It gets colder because your going farther and farther away from the sun. If you go to low and get to cold, you could end up getting Hypothermia. Though Hypothermia is not major, you just need to keep yourself warm so your core body temperature can reheat. Anyways back to the question, say for Instance that the Sun somehow was never here on earth or just Vanished somehow. Everyone will get Hypothermia and they will need to reheat they Core Body Temperature. Most wouldn't survive because it would be to cold. So, to answer your question, the temperature, Decreases.

                                                                                ~Journey~