Floods

I would not only worry about the water but also the boys and girls in blue!

www.legislation.gov.uk/ukpga/1988/52/section/36

Imagine if you get in a pickle and they are called to help. They'll do you for contravening the sign!

Kirkynut

Also what if the water is hiding something significant for instance that the road is actually washed away and is now 10 feet deep, or there are some foot high boulders just under the surface? If you want to go for a play go to a designated place where there are marshals being paid to look after you, don't do it on a public road where some poor members of the emergency services have to come and save you instead of someone who is in real need through no fault of their own. Public roads are only shut off for a good reason, namely the protection of the public.