"Sit on top" kayaks place paddlers in an open, dimpled deck above the water level. This style is typically used for non-whitewater activities, as most people find it difficult to stay inside the kayak, while also preventing the kayak from "rolling", allowing the user to stand upright if they roll over. Sitting on top has some benefits, such as being able to "dry the hatch," a compartment that typically runs the length of the kayak where, in addition to providing more buoyancy, kayakers can store various equipment . "Kayaks" sitting on top often use "through holes", which allow all the water coming in on the boat to drain through the deck and dry out. A "cockpit style" or "spray skirt" creates a watertight seal at the waist. There are a variety of "cockpit" boats that generally allow the user more control over the boat due to their ability to push against the walls to tip over to complete the maneuver. A common variant of "cockpit style" kayaks are "cruise boats", which are usually very short kayaks in which the user can perform tricks and maneuvers: "inflatables" are a hybrid of the first two configurations. These boats have an open deck, but the paddlers sit under the deck. These boats are often more unstable due to their higher position in the water. They are often used in a more commercial setting and are often affectionately referred to as "Duckies." The "tandem" contrasts with the distinctive design of most kayaks, which are configured for multiple paddlers. Tandems can be used by two or even three paddlers.