The iPhone 7 and iPhone 7 Plus are the first two iPhone models to be listed as "splash and water resistant" by Apple. Both models both carry an IP (Ingress Protection) 67 rating. This means the iPhone 7 and 7 Plus can be immersed in liquids up to 1m for up to 30 minutes, however, it is ill-advised to take your iPhone for a swim or into the ocean.
The iPhone 7 is "water resistant," not waterproof, and liquid damage is not covered under Apple's warranty. Apple also warns that the "splash, water, and dust resistance are not permanent conditions and resistance might decrease as a result of normal wear." This means you run the risk of destroying your iPhone by purposely submerging it in water, and might get stuck shelling out more money for a new device.
This does not mean you can't take underwater photos. Since the iPhone was tested and proven to withstand accidental water incidents up to 30-minutes, it is possible to snap a quick photo in shallow water. However, like we said we can't recommend it, andat no time should you take it scuba diving or use it under water for any length of time. If you value your iPhone, the best policy may be to act like it is not water resistant at all.
There are a variety of waterproof cases that promise to keep your device safe from water damage, but most are designed for older models that are not water resistant.