TRS to RS232

Hello, I am designing a sensoring package to be used in a design project for a class which is a graduation requirement. The project is to design an autonomous surface vessel that can be launched from an 18ft RIB boat by two people. It needs to be able to navigate a 1 mile river and perform surveillance and reconnaissance, and stream live data wirelessly to a receiving station. As such, we have decided to put a shotgun microphone on the vehicle. because of the size of the vehicle, all electronics need to be in either RS232 or analog format. The microphone outputs to a standard 3.5mm headphone jack( TRS?). Could anyone point me towards a TRS analog to digital converter (ADC), or suggest another method such as doing software data processing of the analog voltages once the raw data has been transmitted to land? Thanks for any input as this has turned into a major problem, and I apologize if this is in the wrong section.