I and my little son built a small electric boat from a kit. However, the kit only offered turning on the motor with a switch, and let the boat cruise wherever fortune it may take.
I thought why not improve it a bit by adding some RC capability. I had some left over toy quad copter remote controls, and decided to use them by building the receiver side out of an 3 $ Arduino mini knock off and the popular NRF24L01+ chip.
rcgroups.com forum user bikemikem added some receiver functionality  to the popular nrf24-multipro project by goebish . I made some small adjustments, and the final firmware is attached to this post.
The wiring between the Arduino and the NRF board is shown below. The motor is PWM driven with some random FET, and the whole thing is powered by some old phone battery underneath the connection board. A single servo is used for steering.
The “Bayang” protocol is used by a lot of different models. The following picture shows a few:
* Eachine H8 Mini (top left)
* Bayangtoys X9 (top right)
* Floureon H101 (bottom left)
* Devo 7E with Deviation  and NRF module
Project by Markus Gritsch at DP forum.