Watercraft fin

A fin for a watercraft comprising:

• a substantially planar member having a first side surface, a leading edge, a second side surface opposite the first side surface, a trailing edge opposite the leading edge, and a base providing an area for attachment to a watercraft surface by either mechanical means or permanent bonding, wherein the leading edge and the trailing edge intersect at a fin tip;
• at least one flexible spine having an elongate body with a top side, a bottom side, a first end spaced apart from a second end and peripheral edges joining the top and bottom sides such that a spine width associated with at least the top side is greater than a spine thickness associated with the peripheral edges, each flexible spine is molded from a composition of fibres and resin using a continuous molding process;
• and
• wherein the at least one flexible spine is bonded to be fixed between the first and second side surfaces of the fin;
• and
• wherein the number, placement and size of the at least one flexible spine between the first and second side surfaces of the fin, provides the fin with a customised dynamic flex pattern and strength.