uwvid

Hi. We have a video camera (Composite SD, 700TVL) mounted on a diver. The signal is transferred via coax. How can we connect it to a monitor and keep the best quality? As of today it is connected via RCA (yellow plug). The RCA is spliced with the coax. Question is ; Will the image improve by using BNC connector, or rather, is there any loss in quality by using RCA ?