People used to "doodle" a lot during meetings when lack of attention or boredom set in.. I thought of that while looking at the sea grass that was washed in by the incoming tide and left behind as the tide receded. Depending on your state of mind that day and the angle that you view the sea grass from, they can be "doodles".. Here is an example: walking along with eyes downcast, I came upon this:
"Ahaaa!" the imagination said. "A sailboat." Therefore after minor tweaks, here is the final image:
Can you see it?