Concept-to-Prototype Mechanical Assembly

The objective of this project is to develop a underwater mechanical scanning sonar system capable of retrieving the full echo response output from the single beam echo sounder device. This device is intended to use in shallow waters such as ponds and lakes of max depth of 20 feet. The range covering is targetted at 50meters.
The system will use a Single beam sonar device (Transducer + integrated processing electronics to produce full echo profile output) with 500KHz frequency and narrow beamwidth.
The device is mounted on a base using a stepper motor and will rotate from 0° to 180°, obtained full echo response at each step. These measurements will be stored on an onboard memory of the controling unit like Raspberry Pi. The sonar device will be in the water for not more than 15mins. It will be removed from the water after 15mins of its duration underwater or predefined number of scans.
The whole system should be secured with an IP68 rating waterproof enclosure. This power source for this entire prototype (Sonar device, stepper motor, raspberyPi etc..) should be LIthium battery pack.

The main parts of this prototype are:
1. Single beam echo sounder such as Blue robotics Ping2, or Cerulean S500 .
2. Stepper motor and driver.
3. Raspberry PI for controlling the stepper motor and the sonar device. Storing the echo output on the onboard memory.
4. Waterproof enclosure.
5. Battery functionality upto 8hours.
6. Any other required accessories/hardware parts.

Note: Seeking local professional in and around Connecticut State, USA.