Vlieland offers 20 kilometers of beautiful sandy beach bordering the North Sea. Of course swimming is allowed there but it is not without danger. There are usually numerous sand banks just off-shore which run parallel to the sand dunes. The sand banks are interrupted at irregular intervals by fast-flowing rip currents which pull you out to the sea. It is important to avoid these fast flowing currents, especially at out-going tides and during off-shore winds.
If you are not an experienced swimmer it is strongly advised to not venture further out than waist-deep.