Once you've waited a day or two and think you've successfully dried out your iPhone, you can try switching it on. If it still doesn't work, or if you want to get the internals checked out, you can ask Apple to take a look, but bear in mind that iOS devices have internal liquid detectors, so there's no point pretending the device went wrong of its own accord. They will know.
One final warning: a bad submersion may cause long-term damage, particularly to the battery, that only becomes apparent months later. In one famous case, an iPhone 3GS spontaneously overheated more than a year after being dropped in a pool. The owner had used the rice technique and the iPhone had worked fine afterwards.
How to avoid iPhone water damage
Apologies if this sounds patronising, but step one is to keep your devices dry. Water's not, you know, good for iPhones and iPads.
We're all human and things get dropped, so it's best to anticipate this. If you really want to use your iPad to read ebooks by the pool or in the bath, consider buying a waterproof case: Lifedge has a £99 iPad case that can handle water and shocks; it also includes an anti-glare screen for sunlight viewing and doesn't restrict the functionality of the touchscreen or cameras. Also consider the LifeProof Nuud case.
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