Marine helmets are part of the Marine armor set in game.
It can be crafted, or found on incoming pirates.
It is the best-protecting helmet in-game, surpassing that of the other 2 helmets. It also covers the eyes, ears, nose and jaw, as opposed to just the head. Moreover, it provides protection against heat damage such as burns.
It is also one of the most expensive helmets. It requires 40 plasteel and 1 advanced component to craft. This is comparable to that of a plasteel advanced helmet, which requires 75 plasteel and 2 components to craft. While the marine helmet has better protection, the plasteel advanced helmet has higher HP and thus lasts longer.
In 0.19/1.0 it received a recipe change and a rename.