Golf course in SZ, now that’s cool 
and you want to find out/monitor the volume of irrigation water.
Yes, I have some experience but that is a sailboat. I modified a RC Laser and did some tests with the amazing developers here at Ardupilot for Wing sails. Here is the latest post I did last year.
Not relevant to your project. However, I can give you my ten cents of experience here:
This is also still confusing to me as well. When searching for the frequency bands allowed for hobbyists around the world, sources like ITU you can learn things like 900 MHz for US and AUS and 433Hhz for EU. But I have not seen China mentioned in any of these list. So digging a bit deeper of the China frequency bands and their usage, I have found (right or wrong) both 900 and 433 bands pretty harmless to use. used for garage opening applications etc. I have also found that that the 900 bands are much more noisy than 433, so I mainly use 433 in my planes and helis. However the boat you see above use a pair of RFD 900x from jdrones. If they had a unit at 433 MHz I would use them all over but they don’t.
If any one here can enlighten us about what RF band is okay to use - please do
Lastly about what RTU boat to use, search the forums for Mapping a lake … for ideas.
Karl