The bucket coolers work well if
you get the details right. I made one last year and gained some insight - ie I substituted a different fan and it didn't move enough air to be truly awesome. Also this ends up being a somewhat expensive project - about $200 depending on how you power it.
The fan needs to move enough air to replace the air volume of the tent every few minutes (3-5). I used a 90-100 cfm fan in a 10'x9' tent that's about 6'6" tall. It produced cold air just fine - just not enough of it to fully cool the tent. For this summer I'm either using this fan: Amazon.com: Delta Electronics AFB1212SHE-CF00 120x120x38mm Cooling Fan, 190.48 CFM, 55.5 dBA, 4100 RPM, 1.6 Amp, 4+3-pin power & TAC connector: Computers & Accessories
or this fan: Fan-Tastic Endless Breeze
As Jbrebe said you need the right amount of Amp hours for the fan and the water pump. This leads to a decision about whether to go solely with a larger battery (simplicity) or to go with a smaller battery and a solar panel (more complexity but indefinite life). Partly this depends on how many hours a day you want cooling for and how many days at a time you will be on the river. I used a 14W folding solar panel and a 18 Ah deep cycle SLA battery - that ends up being about the smallest combo that works - unless you have cloudy days - this relies on recharging everyday and getting sun while you're using it. Otherwise then you would need a bigger battery and/or solar panel. Many people choose a 105 ah deep cycle marine battery from Costco (you probably won't need a solar panel with this large of a battery for trips up to a week long).
I highly suggest reading this thread from here: https://eplaya.burningman.com/viewto...=2670#p1015937
Also you might want to read some lessons learned here: https://eplaya.burningman.com/viewto...=3030#p1058444
Good luck and have fun!