Not enough robots are used in the fight against ocean plastics. Remotely-operated vehicles (ROVs), controlled via telepresence, can collect ocean waste, but underwater depth perception is challenging, especially for transparent objects like plastic bottles on 2D screens, where augmented visuals could assist. This study investigates stereo vision technology for underwater depth estimation, focusing on transparent objects. We recalibrated a stereo camera for underwater applications, testing depth accuracy on air- and water-filled plastic bottles under controlled lighting. Results show that recalibration improves depth perception for opaque objects but remains limited for transparent materials, particularly water-filled bottles. Our approach and performance analysis highlight the challenges of accurate depth mapping for submerged plastics, underscoring a need for advanced methods to achieve reliable augmented visuals.