Step 1: Start with crafting the Oxygen bottle/Flippers.
Step 2: Whenever the Oxygen bottle or the Flippers are used or when the durability of the item has decreased, pull the item out of the equipment slot.
Step 3: When you've pulled the item from the slot, the item will still be damaged. But don't worry, Step 4 is going solve everything.
Step 4: Then you put the item back into one of the equipment slots, and the item will now be restored to full health and in pristine condition.