This is the helmet used to dive underwater. If you take it off while under water, you will lose HP. There is a 5,000 gp deposit for the helmet. You must be a member of the Explorer Society and have at least the Rank of a Relic Hunter/Huntress to rent one (Beginning of the The Undersea Kingdom Quest). Very useful to hunt Water Elementals with it, since it blocks the strongest (drown-based) attack of them. Note: Speed bonus will disappear temporarily when you put it in backpack/floor or travel to city.