Photography from on Top of the Water
Shooting from a small boat has its limitations. The boat is always moving so you cannot use a tripod as this will transmit all of the boat's movements to the camera. So you will be shooting hand held, and because of the boat’s movements, you must shoot at a faster shutter speed than when you are on land. The general rule of thumb is that you shoot at 3X the shutter speed that you shoot hand held on land. If you are shooting with a 200mm lens then the minimum speed that you would shoot on land, without Image Stabilization is 1/200th of a second. (remember the ‘1 over the focal length’ rule of thumb?) On the water this is then moved to 1/600th of a second. Image Stabilization will help but it will depend on your camera so you will have to experiment; remember it is better to err on the too fast side rather than too slow.
The movement of the subject will also have a bearing on your shutter speed. Hand hold the camera the way that you hold a rifle, hands cradling the camera, with one on the lens (thumb out) and the other holding the camera with one finger on the shutter. Use your knees to float with the boat's motion keeping your upper body as stable as you can. Next you need to find a spot that is as steady as possible; this is at the rear (stern) of the boat. I know this because it is also the best place to stay if you get motion sickness! :-))
If you are photographing something in the water then focus may be of concern. If the subject appears and disappears from under the water away from the boat then you need to focus on a spot about half way from an acceptable distance shot and the closest that you can get the whole subject in the frame. Dolphins are a good example of this; you are never sure when or where they are going to surface and what they are going to do. If they are running with the boat's wake, then it is easier to keep the animal in your frame and squeeze the shutter when they come up for air. If they are jumping away from the boat then you have to look from above the camera and then move the camera up to your eye as you see the subject. By having the focus set at an in between distance you give your camera a better chance to focus on the subject.
Some subjects are very easy to shoot as they stay relativity still and do not move very fast. Icebergs are an example. Larger subjects like icebergs are static and stay still most of the time. Icebergs will calve so you should always be on the alert for a loud CRACK as a piece of ice breaks away from the main berg and there is a big splash as the piece falls into the water.