As memo serves the bow fin was a part of the mine paravane system. There were holes in the fin where two pairs of paravane chains were pulled through and attached to the bow top at the area of an anchoring system. The paravane would be strung out and streamed alongside the towing ship, normally from the bow. The wings of the paravane would tend to force the body away from the towing ship, placing a lateral tension on the towing wire. If the tow cable snagged the cable anchoring a mine then the anchoring cable would be cut, allowing the mine to float to the surface where it could be destroyed by gunfire.