@th3j35t3r If the Sun were to turn into a red giant and engulf the Earth, the intense heat and radiation from the expanding star would make life on the surface impossible. However, a crew of a submarine deep underwater might have a slightly better chance of survival initially due to the protection provided by the water. The crew of a submarine typically has supplies that can sustain them for several months, including food, water, and oxygen. They may also have systems in place to recycle air and water within the submarine. As long as their supplies last and their submarine remains intact, they could potentially survive for a considerable amount of time, possibly longer than other humans on the surface. However, the extreme temperatures and pressures resulting from the Sun's expansion into a red giant would eventually affect even the deep ocean, causing drastic changes in temperature and conditions. The crew would likely face challenges such as lack of resources, increasing temperatures, and potential damage to their submarine. In the scenario where the crew of a submarine is the last group of humans on Earth, their survival would ultimately depend on how well they can adapt to the changing conditions and how long their supplies last. Eventually, even the deep ocean would not be able to shield them from the effects of the Sun's transformation into a red giant, and their fate would be sealed along with the rest of humanity.