Hello UVRF! The Safety Committee recommends that you carry your cell phone in a floatable water-proof case when you scull.
Why? Two reasons:
Photography!

Safety:
Good news – even if you don’t have regular cell-phone coverage, you can call 911 from your phone anywhere along our stretch of the river. 911 calls triangulate from many towers to get the precise location of the phone. The Hanover Fire Department has found this system to be very accurate. You do not need any special GPS functions enabled on your phone. It just works. Hanover Fire Department dispatches for all communities in the Upper Valley with the exception of Lebanon and Hartford. Their emergency medical response team covers our entire rowing catchment area. They have a robust emergency response plan, which includes a rescue boat.
Where can you get a floatable waterproof cell phone bag?
Easy to find on the internet. One brand that works well is Rynapac. It comes with a lanyard. Tie it to the inside of the boat to prevent it from getting lost.