The time will count for time out of the country for your Foreign Earnings Deduction for the seafarer claim however I suspect your onshore earnings will still be taxable, as you are not on a ship.
As you are 50/50 on a vessel and onshore you will struggle to convince the Taxman you are a fulltime Seafarer, you can do other work apart from being on the vessel but it should incidental or in the minority of your employment.
I suggest you speak to someone with more knowledge such as Seatax.
As you are 50/50 on a vessel and onshore you will struggle to convince the Taxman you are a fulltime Seafarer, you can do other work apart from being on the vessel but it should incidental or in the minority of your employment.
I suggest you speak to someone with more knowledge such as Seatax.