One thing that is well known among birds in flight photographers is that Swallows are very difficult to shoot in flight, they are small, very fast and have erratic flight patterns. A first for me this evening was to capture these images of a Tree Swallow diving and playing in the water. The scene is backlit so not the best light but I am a happy camper with these images. I shot these from a kayak.
D810, 500mm F4, 1/1600, F4, ISO 720
In this shot the bird is still submerged in the water as it rises for takeoff.