HI nasraf
I think you understand the principle. Basically its an AC motor driven by sequential pulses to the coils. I use outrunner brushless in my crash tender as this type gives more tork and the spinning mass of the magnets produces a nice smooth power curve. I believe the aero flyers are more interested in the feedback type of motors as brushless can run away and self destruct if run with too small a load Ie too small or detached/broken prop. For model boats this is not such a problem provided you ensure good sound couplings and well fastened propellers. Given the revs you can achieve this is a necessity in any case. At the revs produced efficiency is not really a problem, in fact the speed is far more than required and a little inefficiency will help you control your boat. if you want speed without the weight brushless and LiPo are hard to beat. You can buy motors and esc via ebay from China, I got mine there and prices are a fraction of the cost in the UK. Do make sure the esc will reverse as most wont without swapping two of the three wires. I use one made for a car and provided you can wait 1-2 secs for reverse it works fine.
Good luck with the model
Dave

In my further investigations I came across a very good web site on electrical matters which also includes a lot of battery info. that may be of interest to others.

This is "mpoweruk. com" it is worth looking at.