Water surprise

This is one of those serendipitous images, where you aren't expecting to find a photograph, but one presents itself anyway :)

In case you haven't worked it out, this is of a bottle of water standing on the kitchen worksurface, lit by the afternoon sun streaming through a narrow gap between the branches of a tree.

The strange patterns in the middle of the bottle are what is known as caustics. Caustics are the reflection, refraction or projection of light by a curved surface, most commonly seen when light falls through a drinking glass.