Activating this trainer:
Press F1 at main menu.
Listen for 'Trainer Activated'.
Press desired hotkey. All hotkeys can be changed on the trainer.
NumPad1: Infinite Health
NumPad2: Infinite Food
NumPad3: Infinite Water
NumPad4: Infinite Oxygen
NumPad5: Easy Crafting
NumPad6: Super Swimming Speed
Easy Crafting: While active you can things for free.
Super Swimming Speed: While active you can hold down while swimming to gain super swimming speed.
Unlock more trainer options including updates from here - Subnautica Trainer