Parking Error

The van has a trailer behind it for a boat, so I'm assuming its owners put the boat in at low water, parked up, and headed out for the day.  You would think that boat owners would be more aware of the possibility of the tide coming in, and park somewhere their vehicles wouldn't end up in a couple of feet of water...

I wonder what happened when they got back?

(thanks to MrsCyclops for pointing out I could get the "parking of vehicles and trailers prohibited" sign in shot...)