Diving Helmet (5e Equipment)
From D&D Wiki
|Cost||Armor Class (AC)||Strength||Stealth||Weight|
|100 gp||+2 (Partial Armor) (Special)||15||Disadvantage||55 lb.|
It is an old diving helmet, made of copper, glass, tin, and brass. It is designed to go under the sea, where being heavy does not matter as much. Therefore, attempting to walk around on land while wearing one is very unwieldy. Wearing this armor will grant disadvantage on Dexterity (Acrobatics) or Strength (Athletics) checks related to activities that need usage of the head in some way.
Because it is a diving helmet, the wearer may use a standard action to seal the helmet, granting 1d6 + 9 minutes of breathable air regardless of the external environment; keeping the helmet sealed longer than this time without some additional connected supply of air are considered to be deprived of air. You may unseal the helmet as a bonus action, and the previously mentioned bonus is not granted while the helmet is unsealed. A damaged helmet cannot be sealed.
Partial armor only grants its AC bonus if you are wearing light or no armor. If you are wearing only one piece of partial armor, you are still considered to be wearing your base armor type (e.g. no armor or light armor). If you are wearing two or three pieces of partial armor, you are considered to be wearing the heaviest type of partial armor worn (e.g. medium or heavy armor). You cannot wear four or more pieces of partial armor.