JP graciously shared with us more details of his amphibious NXT. (Photos are copyrighted by JP Brown).
What follows is a portion of JP's email to me regarding his robot. If you have more questions and comments about the robot, please post them here.
JP is willing to share a copy of his .NET program which drives the robot. If there is interest, we'll post the program on the blog.
"The blades enter the water just after the stroke begins and lift out of the water just before the stroke ends.
The main problem was writing the PC end of the Bluetooth link for control. I ended up with a fairly decent .NET control program which can take input from either a joystick or from the keyboard and mouse and then push commands to the NXT.
We tested Rowbot fairly extensively in the bath before we went on open water. As you will see from the photos, the fact that the oars can be disassembled makes transport easier:
The Youtube video shows the maneuverability (of the robot). After about 20 minutes of driving it around the pond we started to get horrible clicking noises and the speed went down to about a quarter. We directed it back to the bank and found that one of the two 8-t gears that drive the robot back-and-forth had come loose, so we decided to call it a day. I've rebuilt that part now, and hope to have another go on Sunday".