Subnautica currently features four different Game Modes.
Freedom Mode Edit
Oxygen and health are the only resources you need to manage to stay alive. Energy is consumed by all electric Tools such as the Flashlight, vehicles such as the Seamoth have their own energy, and appliances such as the Fabricator use energy stored by Lifepod 5 and Seabases.
Survival Mode Edit
Similar to Freedom mode with the addition of needing to maintain your Food & Water levels as well as oxygen and health. If you drown or your health reaches zero percent you lose all of the items in your inventory that were collected without first securing them by entering the lifepod, a seabase, or a Cyclops. Items in storage containers aboard a Cyclops are not lost.
Hardcore Mode Edit
Although similar to Survival Mode, Hardcore Mode restricts you to a single life; if you drown or your health reaches zero percent your game ends, forcing you to completely start over from the beginning. In addition to this, Hardcore Mode does not warn you when you have low levels of oxygen.
In Creative Mode, death, story, hunger, thirst, and oxygen is disabled, materials and Blueprints are not required for crafting, vehicles have no energy requirements and cannot be damaged.