704 - 7/10 - Working on deck in heavy weather - Worldwide
The most important question to consider when planning work on deck in heavy weather must be "is the work absolutely necessary?", if the answer to this question is "no" then it may be prudent to delay the work until the vessel encounters calmer weather or sheltered seas.
If the work is considered essential, weather forecasts and the prevailing sea conditions should be continuously monitored so that ample warning may be given to enable ships staff to secure the vessel and move to a safe area before the adverse or heavy weather is encountered. Accidents have occurred when crew members have ventured out on deck to secure items that were not adequately secured, either prior to sailing or when the vessel was in sheltered waters.
Source UK P&I