First - water is very unforgiving medium. Example :
I have a lot of reeds growing and closing of my private boat channel at home. So we took a good powerful Weed Whacker (Strimmer we call them) with gasoline motor. I drove my motorboat while pal of mine put the strimmer over side to cut. As soon as that blade hit water - the load increased tremendously before we even got to cut anything. In fact it slowed so much - we could only cut at waterline. It will take a lot of power to run props ... What size boat ? Estimated weight ? By the time you have bought powerful enough motor ... a Hand Drill will NOT be enough if you are talking man carrying boat ... and drive components - it would likely be cheaper to buy a commercial trolling motor. We have them over here for about 150 euros and up .... far more efficient and designed for the job.
I'll fly anything if I can launch it ! Youtube : solentlifeuk