The Seafarer Act Article 33

Seafarers shall have at least one regular day off in every seven days, unless the seafarer is taking turns at watchkeeping because of navigation needs.For the case mentioned in the proviso of the preceding paragraph, the employer shall arrange for taking leaves by turns.
中文原文 船員法第33條
船員每七日中至少應有一日之休息,作為例假。
但因航行需要仍應參加航行當值輪班者,不在此限。
前項但書情形,雇用人應另行安排輪休。

English translation for reference only; the Chinese text prevails. Not legal advice.