First recommendation is to look at a lot of professional work. Notice how the shots are put together, how subject focus is made and maintained! See how dolly shots (swimming shots) are mixed with static shots. Also notice how few if any shots involve zooming ! There is a lesson in that!
Now assuming you're on a dive at a new dive site, you can't plan your shooting too far in advance. But what you can do is maintain some camera discipline as your dive progresses. First, equipment allowing, shoot from the moment you enter the water until you surface. Along the way, stop, refocus on close subjects and hold those shots for 5-10 seconds. Also, while shooting, remember the viewers' plane of reference. This simply means that you don't cross the line of action. An example of this would be shooting a fish swimming toward you from the left side and then the right side. Also, make your shots only as long as you can hold the camera steady! It's OK if the fish sway back and forth in the surge, but not the camera!
There are some stock shots which can work quite well for you and these include the descent shot and ascent shot. I shoot descent shots by starting with a reference to the dive boat from water level or slightly below water level if using a colored filter. I then pan the camera down and descend to the dive site. If you can frame other divers descending, so much the better. Passing through the occasional bubbles can make for a nice effect drawing the viewer into the dive.
The ascent shot typically focuses on something the viewer has seen in the last shot and then trails up and away while keeping the camera focused on that area. For example, if wreck diving you may have a long shot of the anchor line on a part of the wreck, followed by a medium distance shot which then you use as a frame of reference during the ascent. I'll finish the shot with a water eye view of the dive boat or perhaps the divers getting back into the boat from on deck.
EditingEditing your footage is the next step and where many people throw up their hands. Editing can be done with a camera and consumer deck and nothing more. You simple cut scenes together using jump cuts, but if your camera work is smooth, that may provide you with many scene transitions on it's own. In any event, you need to scrap the out of focus, jittery and boring segments.
A basic format for editing should include a lead in shot, close up if appropriate followed by the next sequence. For example, a long shot toward a coral head in the distance followed by a close up of wildlife on the coral. That is why you shoot five to ten seconds of stationary footage of objects. Let the subject matter move rather than the camera!
Establishing scale can also be a powerful video technique when shooting large wrecks. Is isn't a bad idea when shooting large objects to try and get an above shot with some divers on the wreck to establish scale for the audience. This is one of the reasons I use the descent sequence to let the viewers see just how big things are!
Music can make or break a home video. If you want to make a so so video really jump, then music might save it! For example, several years ago while diving in Palau, I was shooting Oceanic White Tips (Longimanus). Now these fellows have little in common with reef White Tips. First they are phelagic sharks, found only in open ocean and it is the immense depth of the water near the Palauian walls which allows divers to see these 12 foot plus sharks!
On one shot, there was a large fellow swimming directly in line with me but perhaps 25 feet lower. As he approached, I tilted the camera down until the lens axis was vertical and directly aimed at the sharks dorsal fin. I then rotated around, while somehow managing to keep the camera inline and then tilted the camera up as the shark swam away. The effect was fairly spectacular and immediately reminded me of the opening sequence in the first Star Trek movie of the attacking Klignon Battle Cruisers. The music, if you haven't heard it is very distinctive.
When I got back home, I edited about 12 minutes of my shark footage into one sequence and used (without permission) John Williams' stirring Star Trek Music to open and the hand held motion control effect shark sequence. I played the tape a few weeks later at a local dive club meeting and was rewarded with several wows from the audience.
LightingNothing tends to raise a debate like lighting among underwater videographers unless you include editing systems! That said, please consider the following my humble opinions rather than gospel.
Most consumer grade lighting systems fall into the 25-50 Watt range which is sometimes adequate for closeup and macro work. However, underwater, the fall off of light is very pronounced and can be very disconcerting to viewers who watch a basically green-blue scene light up with colors as the camera approaches the object during dolly shots. At that power range you're pretty well limited to lighting objects in the 6 foot or less range. Beyond that, either the lack of light causes problems or water clarity becomes problematic.
There are essentially two ways to overcome this problem, none of which are overly practical. First, is to shoot shallow, with lots of natural light available and a correction filter which is removed before each lighted shot. The second is to confine the entire video to closeups and macro shots. The third is to only shoot video in extremely clear water and the fourth is to live with the color shift!
Another basic problem with several u/w lighting systems is hot spots. A hot spot is an area within the light cone which is visibly brighter than the rest of the field and worse yet, in most cases this spot in dead center of the light. Before buying a video light, I highly suggest testing it against a wall to look for a hot spot.