I joined a group of researchers visiting the University of Florida for the CUAHSI in-situ water quality sensor workshop during their field day on the Ichetucknee River. They deployed the "HydroSphere," an autonomous bubble-like instrument with sensors at the bottom of the clear dome that measure water parameters such as pH, dissolved oxygen, temperature, depth, and acceleration. It can text GPS and other real-time data to your phone and you can set a time for the CO2 cartridge to activate and fill the dome, sending it to the surface for easy retrieval in bigger rivers. This technology is giving researchers easier access to drifting devices that were previously less common in river research. If you're interested in the science behind these Lagrangian drifters, check out Ensign et al (2017) in Freshwater Science ("New strategies for measuring rates of environmental processes in rivers, lakes, and estuaries").