The present disclosure relates to flow channels comprising a channel length having a first portion approximately parallel to the maximum waterline thickness location of a body and at least a second portion non-parallel thereto, a leading edge at a first end of the channel length, the leading edge separated from a trailing edge by a free edge along the channel length, the free edge projecting a predetermined height from an attaching edge attachable to at least a portion of the surface of the body, and at least a portion of the free edge being arcuate. A method comprises providing the fluid channel attachable to a body, modifying resultant vortices and reducing or minimizing shock formations or separation regions of the freestream.