Swans are probably the most photographed bird on the planet as they have an inherent grace and beauty so taking a photo that lifts above the masses is very hard. I think you have done a reasonable effort here and the lighting is fine. The problem is in the focusing which is not pin sharp and it really needs to be when taking a photo this close. The problem is, by cgoing this close you exacerbate the DoF situation and make it harder to keep the whole head in focus.
Let me try and explain that and apologies if I am just telling you stuff you already know: maybe it will help someone
The apparent camera point is about 6 inches in front of the bird's face: I know it isn't in reality as you were using a 420mm (equivalent) lens and would be mad to get that close! But you still have to calculate your Depth of Field from the apparent point, not from the real point so let me conitnue....
The swan's head and neck from front (closest point to 'camera') to back is about 3 inches in-depth (estimating here so don't try and measure it
)
Ok, so that means the closest point is 6 inches from the lens whilst the back of the head/neck is 9 inches away, 50% further. That is relatively a large area to keep in sharp focus (and before anyone says it, yes I know the actual measurement should be taken from the sensor/film plane but I am just making the point so stop being so picky
)
As you only used F5, you were not giving yourself a fighting chance of getting the whole of the head and neck in sharp focus. I think you could have gone to f8/f11 and still got the body in the BG out of focus enough to give the lovely diffeential focus effect.
I hope that makes sense but well done on what you have got here. The body behind the head makes this a far better picture than simply the neck and head in profile with water behind.
Cheers and hope we can see more of your work soon.
Rob