The insurance provided by this Policy is, (in addition to the risks already covered) extended to cover loss or damage to the jetty, piers, docks, wharves etc, and other sea-fronting or water-fronting properly and or structures insured, directly caused by impact, which for the purpose of this extension shall be defined as accidental forcible contact or collision of or impact by any substantial floating or underwater body or object mechanized or otherwise, with the jetty, piers, docks, wharves etc, and other sea-fronting property and or structures.