Close friend had a brill career in the RANR.
Retired with a brass hat.
As a younger Lt, passed the Navy unrestricted navigators "license" which Authorised him to navigate an RN ship worldwide and enter berth and leave any port without pilot or tug assistance That is a very high level of skill.
Decided with my encouragement to get a Private Pilot license. Failed medical due to color blindness.
So he can operate an Australian Naval ship anywhere in the world but was proscribed from flying.
Didn't persist and gave up the idea as too hard.