I am new to editing, but it a lot like editing writing, nobody wants to cut their baby. Try to focus on scenes that drive the narrative. The surface shots right at the start of the video sets the scene. Going down the anchor line takes the viewer to the setting of the story. A fly by of the stern or bridge is great, but how long should it be? Look just for that moment when you felt like "this is the best feeling I felt on the whole dive" and delete everything else. Cut to the scene where you are heading back up anchor line, fade to black. Add music to set the mood. A red filter to add more color might be a good investment, mine was $30 at the LDS. The sites are interesting and have some history, why not add some commentary about that? When did she sink, what were the circumstances? what was her cargo?