Five initially. But only if both the first and last day involve more than 7.5 hours at sea.
Straight from AMSA: A dayis a minimum of
No maximum(other than 24 hours).
Days at sea are days at sea. Generally, you can't claim more than one day for a single
Additional sea service (10 days) is credited for
each full 20 days accrued on extended voyages:
• An extended voyage is a voyage:
- of more than 24 hours duration;
- including periods underway in a watch
keeping capacity or undertaking deck duties in both day and night;
- when fatigue is managed in accordance with the STCW Convention.
So you may be able to get a bit more credit if you have enough extended voyages.