US Patent 10046836 Retractable fin and fin box

A retractable fin system having a retractable fin and fin box is disclosed. An example retractable fin system includes a housing insertable into an opening in a watercraft board. The example retractable fin system also includes a retractable fin. The example retractable fin system also includes a bias to maintain the retractable fin in a default outward position from the housing. The bias retracts the retractable fin into the housing on contact with an outside force.