经查证，海上保险中的“marine extension clause”，可以译为“海运扩展条款”或者“航程延长条款”。据百度百科介绍，是指船舶保险合同中规定假若保单期满，被保船舶因某种特殊原因未到达目的地，只要被保险人事先通知保险人，可以继续加保到抵达目的地为止的一种条款。有时被保船舶在保单期满时，由于某种特殊原因仍在海上航行或停留在途中避难港，按照原合同，保单到期，保险人责任自然终止。延长条款就是为了满足海上船舶保险人的这种特定需要而制定的。按照该条款规定，如果保单期满时被保船舶遇到以上情况时，只要被保险人事先通知保险人，则被保险船舶可按比例计算其保费，继续加保直至到达目的地为止。

海上保险中有关“marine extension clause”的规定如下所示：

This insurance specially to cover the goods during:

i. deviation, delay, forced discharge, reshipment and transhipment;

ii. any other variation of the adventure arising from the exercise of a liberty granted to the ship owner or charterer under the contract of affreightment.

In the event of the exercise of the liberty granted to the ship owner or charterer under the contract of affreightment whereby such contract is terminated at a port or place other than original insured destination, the insurance continues until the goods are sold and delivered at such port or place; or, if the goods be not sold but are forwarded to the original insured destination or to any other destination, this insurance continues until the goods have arrived at final warehouse as provided herein.

本保险特别承保以下期间的货物：

i. 绕航、延迟、被迫卸货、重新装运和转运；

ii. 因船东或承租人因行使其在海运合同项下的权利而变更航线。

在船东或承租人行使其在海运合同项下的权利的情况下，如果该合同在原定保险目的地以外的港口或地点终止，则本保险的有效性持续至货物在该港口或地点出售并交付之时；或者，若货物未出售但转运至原定保险目的地或任何其他目的地，则本保险的有效性持续至货物抵达本保险规定的最终仓库之时。

来源：

百度百科；

https://www.cki.com.tw/Content/files/%E4%BF%9D%E9%9A%AA%E5%95%86%E5%93%81/%E8%B2%A8%E9%81%8B%E4%BF%9D%E9%9A%AA/%E8%B2%A8%E7%89%A9%E9%81%8B%E8%BC%B8%E4%BF%9D%E9%9A%AA/1311-MARINE%20EXTENSION%20CLAUSE.pdf