"Maybe you can improve your power using an other propeller (change size or pitch) or a 4 cell battery (15 V), if your brushless controller / motor supports it."

"The new boat looks really good. You almost convinced me to build one for myself. How fast can you drive while logging the data? How long is the battery life?"

"You can combine this with DrDepth: http://www.drdepth.se/ . It generates depth maps form GPS+Sonar data."