According to Missha's webpage:
Main Ingredients: Deep Sea Water + Sea Weed Extract + Mineral Water
As a fresh and moist gel that contains deep sea water, it is quickly absorbed into the skin. By providing a lot of moisture to the skin, it not only causes make-up to evenly stick to the skin but also keeps make-up fresh all day.
What is DSW (Deep Sea Water)
Sea water that is more than 200 meters below sea level and that has been preserved in low temperature, high pressure, and has not contacted with air or sunlight in a thousand years. Pure and clean water without various pollutants or bacteria and is rich in mineralsas well as essential elements that has excellent hydrating and purifying effects.
I mainly use this to thin out my foundation, I had this Ipsa full coverage liquid foundation that is really thick, and I just can't wear it on its own because it gives me that mask feeling, so I use this fitting gel to thin out my foundation and make it wearable.