What I had dismissed as a particularly creepy looking seagull from afar soon revealed itself to be a Caspian Tern. They are much more pointy looking, giving off a predator vibe instead of a scavenger vibe. They would fly back and forth along the waters edge constantly darting their head around looking for fish. When they finally spot something, they do a full on dive right down in the water in order to catch their prey.
This is that dive.
I got this with my 150-600mm lens, shooting at 1/1000 and f7.1. An ISO of 1000 was needed to make sure I had the fast shutter speed, as it came in hot.