Hello,
here is my idea (I actually wanted to realize it since long time!):
building one or more floating explorers (easy done with a plastic bottle) to explore rivers.
Thanks to the Electron + GPS + a few sensors + battery and solar panel, we could monitor river stream speed and also some other health parameters, like temperature and maybe water oxygenation or other chemical data.
The Electron could send its position plus data measured every 15 minutes to a receiving station which would collect data and elaborate them for the public.
Given the affordable cost of the materials, the loss of one explorer wouldn’t be too severe. Also the GPS would help find any stranded “boat” if necessary!
Finally a message on the bottle would help it return home if found by someone else. 
Here is my concept in picture:
I hope you like it!
Andrea