In general the readings will not be underwater. At best, I think we could cover a foot or two with RF before the signal fades to noise. Even though sound travels well underwater, RF at these frequencies do not.
But what we hope to do, is take them out, leave them sealed and then download the information via a stored CSV file. That is the part we are struggling to code with right now.
We are building one to ride on surfboards that has gyrometric and accelerometric capabilities as well as temperature using a sinple DS18B20 tail into the water. This is for a social science project.
However, a more involved project involves pressure, temperature and conductivity (this is the hardest one to reliably measure with affordable parts).
the whole shebang is used to monitor streams, rivers and as of late wells to assess the impacts of salt run-off and ground water infiltration. Currently the commercial units cost $1500 plus a reader per single instance. If we can get this to work we can install 10x the number of sensors and engage citizens and science teachers in the building of our network.
Right now, I am trying to make it easy to get files out without the help (who might be 10 or not technical) having to open the units and reassemble them properly. Thus the WIFI.