Background: Hybrid aerial underwater vehicles offer aerial access and submerged inspection, but fluid loading, buoyancy, enclosure integrity and changing control authority complicate their development. Objective: This study developed a reconfigurable quadcopter architecture and examined the mechanical and system integration requirements governing its intended aerial and underwater operation. Methods: Three dimensional computer aided design and engineering drawings guided component selection, additive fabrication and preliminary assembly. Four brushless motor channels, stepper actuation, an enclosed central body and a Pixhawk controller were integrated into the architecture. Analytical relationships for thrust, hydrostatic loading, buoyancy and actuator allocation were formulated to interpret design constraints and define subsequent validation requirements. Results: The development produced a CAD configuration, printed components and an assembled four rotor prototype. Assembly exposed joint alignment and sealing difficulties that required iterative adjustment. The analytical assessment indicated that propulsion speed, enclosure loading and thrust direction must be coordinated across operating media. Increasing immersion depth raises hydrostatic pressure, whereas increasing propeller diameter strongly affects thrust and shaft loading under constant coefficient assumptions. Four independently commanded rotor channels cannot provide unrestricted instantaneous control of all six body force and moment components. Quantitative flight, submerged locomotion and transition performance were not established. Conclusion: The study provides a preliminary mechanical architecture and a physics based framework for developing reconfigurable aerial aquatic quadcopters. Experimental validation remains necessary to establish propulsion compatibility, enclosure integrity, buoyancy stability and transition repeatability. Future work should combine calibrated measurements, mechanism characterization, mode specific control allocation and repeated bidirectional transition trials under controlled conditions.

Keywords: hybrid aerial underwater vehicle; reconfigurable quadcopter; aerial aquatic robotics; mechanical design; system integration; transition control