Here's a picture of the electronics. The battery and ESCs are overkill for the two tiny 140 motors, but I wanted to reuse the ESCs in a larger sub in the future, possibly driving dual 540 motors! If the battery ends up being too heavy for my hull size (i.e. it sinks my sub), I'll just use some AAs instead! That pack is a standard 6-cell SC stick pack. I have just a 2ch AM RX with an airplane elevon mixer controlling the ESCs. I disconnected the power wire on the RX connector of one of the ESCs so the BECs don't fight each other.