You'll need a case
Your phone is important, no doubt it runs your life, if its gets wet, it will stop working, and they definatly dont float. We've verified they dont float, so be careful!. You've got a couple of options here, either a high quality (and price) case that lasts years, or a cheaper, ebay style case, that you'll probably buy a couple of over the course of the year. Everyone seems to have their own ideas of cost vs many cases, but its something to think about. At Rowlytics, we typically use cheap ebay cases, and lots of them, replacing them often. We'll often end up taping them, gluing, and other weird things, so we're often not too insterested in a big investment.
The first thing your case needs to be is waterproof. We're not talking just waterproof around the switchs/buttons/plugs, but the whole phone. Water, and especially salt water is super efficient at finding its way into electronics. You'd be amazed at how a little splash can quickly ruin your phone.
There are three types of cases available for most phones
The cases are made from a perspex or other similar hard plastic. They'll have a gasket around the case opening and snap lock to ensure the case stays shut. Typically they also make your phone shock resistant, and some of them even give you the ability to plug your headphones in. Hard cases are great if you want to ensure your phone is always mounted exacly the same way (good). You can also potentially permanently mount the hard case to your boat (screws/bolts) this makes mounting and removal very quick and simple. Drawbacks? most hard cases dont allow you to interact with the smartphones screen. You'll need to do this to start and stop our app.
Zip lock case
These types of case are like a smapp plastic bag with a series of zip locks that when locked, and rolled over onto themselves, provide a very water tight seal. Typically these case can handle many meters of submersion in water. This kind of case normally allows you to interact with the touch screen. These cases are normally very cheap, but are known to form tiny holes in the corners with wear, so do check them every now and then. Typically you'd remove the phone and case after each session, via velcro or a similar mounting mechanism.
Wrap around, glove case
These cases are like a semi hard glove for your phone. They fit your phone perfectly and cover it entirely, allowing you to still use the touch screen, but also have the advantage of perfectly fitting the phone, so theres no chance it can slide around. Some of these cases also come with mounting brackets attached to the backs of them, which makes mounting and removal extremely easy. Make sure if you get one of these cases, its "waterproof" and not just "splashproof" our water sports require more than splashproof!
Worried that your phone may fall off into the water? You may potentially like to attach a float to your case incase something bad does happen. This gives it the ability to float for a bit while you retrieve it, far easier than trying fish it from the bottom of the river.