Might the cracked bill indicate an injury? Otherwise, this bird looked fat and healthy. There was a trace of blood on his neck, but the water could have washed more away. No injury to his feet or wings that I could see.
The "crack" in the gannet's bill is actually a perfectly natural articulation point. Look up the many gannet images posted to BPN and they will all show the same feature. Relatives such as cormorants and shags also have it. The line in the lower mandible is just the border between the bill and the skin of the gular pouch.
In our beached-bird surveys in the Maritime provinces of Canada we sometimes find gannets, so this is not an uncommon occurrence. In our neck of the woods the most common cause of death is drowning in fishing gear (seine nets) set for Herring.
Thanks for the inform John. I have seen the "crack" in images, but I was surprised to see how jagged it was. I looked at this bird's feet and wings, no sign that it was tangled. Such a shame.