And the need to go to the Admiral is to make sure this rather drastic step of ordering someone not to sail from a nice harbor on a nice day because of what might happen later at sea, isn't overused of taken in haste by some Lieutenant down on the waterfront. Usually Admiral follows the recommendation of the Captain of the Port, who knows his/her Lieutenants.
Yes I guess it has similarities but here a Port captain is never a lieutenant. We have a different terminology, here a Captain is always a Navy officer and also one that is a rank to be Captain of a ship have a look:
As you see there are several Captains and the lower one it is Capitão Tenente that corresponds to a Major in the army. Normally Captain-lieutenant are in charge of smaller ports and on bigger ones the rank is Capitães de Fragata (over on the hierarchy). No inexperienced lieutenants in charge, all experienced seamen and probably is why they don't have to have authorization from an Admiral if they think something requires their ruling in what regards safety.
On the merchant ships "Captains" here are Comandantes (commander) and on fishing boats or small boats Mestres (Master). On private boats they are Patrões (Boss). Were we have to have licences for commanding private boats over 7m (Patrão). Under that you need only a Sailor's licence (Marinheiro). There are 3 Patrões licences, Local, Coastal and Deep sea (unlimited).
Well, complicated but you have to remember that our Navy is almost 800 years old and names and titles come for a long way and that tend to make things a lot more complicated