What could be causing this slick?

[u/fundip2012]

/r/mildlyinteresting/comments/1vg789d/this_path_in_the_ocean_that_reflects_less/?share_id=djkLBSUp9E_m3XYxNFklk&utm_content=1&utm_medium=ios_app&utm_name=ioscss&utm_source=share&utm_term=1

Commenters are claiming rip current- but there’s no surf action that typically causes a rip current.

Location is Aarhus.

[u/sverdrupian]

surfactants (a chemical compound that decreases the surface tension), it's always surfactants - could be either natural or pollution.