This Sea Lion photo was shot at the Central Park Zoo. The trick here is to frame your shot before the Sea Lion swims into frame (the photo was framed in camera, not cropped). You predetermine where you want the edges of your frame. I positioned the camera to take advantage of the nice V shapes at the top and bottom of frame.
Choosing a downward angle also removed distracting elements from the background, like spectators and buildings thus making a cleaner shot and keeping the viewers attention on the Sea Lion. Using your camera’s S or TV setting (Shutter Priority, Time Value) you predetermine your exposure settings. I chose a shutter speed that gave me a little bit of blur (1/60th) to accentuate the action, but not so slow that the Sea Lion appears as an indeterminate blur in the water. I also set up the the flash to fire, brightening up the Sea Lion in the water (set camera to Forced Flash On, as opposed to Auto). Because the glass angles away from camera I didn’t have to worry about flash reflecting back into camera. Then you simply wait until the Sea Lion swims into the shot. This may take a couple of attempts until the the animal is in the right position. Be patient.