WHAT IS ART?

Here's a little exercise in art appreciation.
Three of the following five pictures were downloaded from the internet whilst browsing. I won't disclose the artists' names. The remaining two pictures are of a different provenance: one which you may find surprising. 
Can you guess which fall into each category? 

Images one, three and four were taken from the internet, having searched for 'abstract art'. Images two and five are photographs taken by my wife, Jane, of fishing-boat hulls at low tide in Bordeaux Bay. 
An interesting comparison.