Interesting project. Difficult to give advice on the info available. Looks like a steerable powered nozzle at the rear but what motor is it and what are the specs?
An Esc does all the hard work and converts the rx pulses into usable power.
I have arduinos and they can be programmed to control the power and rotation of a motor but would need additional high power Mosfets as well as other circuitry to buffer the unit from the output.
If you are really into arduinos then a walk in the park but I believe an ESC would possibly be more robust and waterproof.
It would be good if you were to post a build blog of your progress as the subject is certainly different to any models we have seen to-date.
Good luck with the build