The Frisian Islands are barrier islands off the coast of the Netherlands. Between these islands and the mainland, there is an area called the Wadden Sea. This sea is only wet in some places, at some times. Instead of being a proper body of water, it's speckled with shallow pools, wetlands, mud flats that flood and dry up depending on storms and changing tides.
That geography makes the Frisian Islands, including the island of Texel, a great place to go beachcombing. During high tides and storms, water from the North Sea flows into the Wadden Sea through inlets. Not all of this water flows back out again, some evaporates. And water isn't the only thing in the North Sea. Wander the mud flats after the tide goes back out and you'll find all manner of random things washed up on Texel's shores—from buckets and signs, to bottles stuffed with anonymous letters.
On a more practical level, current patterns in the North Sea push whatever is in the water towards Texel. That means when a container ship loses something like a box full of luxury coats, the beaches of Texel are a great place to find it again. All that flotsam and jetsam (both the useful and the whimsical) helped create a culture of beachcombing on Texel. For generations, people went down to the shore and finders-keepers was the name of the game.
You can watch a new 14-minute documentary on Texel beachcombers and the goodies they've found. It's called Flotsam & Jetsam and it's available on Vimeo and it's really interesting—a great example of how the realities of nature and science can shape the way culture develops.
Read a geosciences master's thesis that explains in more detail how the tidal mud flats at Texel work.