The Apple Watch comes in three collections and features two case sizes: 38 mm (1.5 in) and 42 mm (1.7 in) spread across 38 individual models in three "collections".[36] The case of the watch includes a mechanism to enable the straps to be interchangeable. For input, the watch includes a "digital crown", which can be turned to scroll or zoom and pressed to return to the home screen, and a touchscreen that features Force Touch technology, which makes it pressure-sensitive and capable of distinguishing between a tap and a press.[6] The watch also has a side button which can be used to display a list of contacts, or access Apple Pay.[37] Apple rates the device's battery for 18 hours of mixed usage.[6] Apple Watch is charged by means of inductive charging, using a cable similar to the MagSafe cable from Apple's MacBook family of laptops.[11] If the watch's battery depletes to less than 10 percent, the watch will enter a "power reserve" mode, which allows the user to continue to read the time for an additional 72 hours. The watch then reverts to its original mode when recharged.[38]
Apple does not explicitly market Apple Watch as being waterproof, stating that it can withstand splashes of water (such as rain and hand washing), but does not recommend submersion (IPX7). However, external testing by The Iconfactory and others revealed that Apple Watch can function when submerged in various conditions (such as swimming), although its touchscreen experiences "erratic" behavior when submerged. Additionally, usage in water may void its warranty, constituting "damage caused by [use] outside Apple’s published guidelines", and apps taking advantage of this may not be allowed per App Store policies which forbid the publishing of apps that encourage users to use devices in ways that may damage them.