High Watermark (HWM) is the term used to describe the system that governs your max gear score after you hit level 60. Once you reach level 60 you will have to grind to increase your Gear Score from 500 all the way up to 600. The HWM will increase for each armor piece (e.g. head armor, chest armor, ring, etc.) and weapon type (e.g. sword, hammer, musket, etc.) that is dropped. Each drop increases your HWM for that item type when the item drops, meaning you don’t have to pick the item up to get the increase.