From Redwall MUCK Wiki

Holt Nauta as it's named and the ship that goes with it were all founded by the adventurous Captain Pontus when he realised an outpost needed to be placed upon the sea to control the recent surge in pirates.

Only beasts who can handle living upon a hidden island can make it into either his crew or on the island itself.

He's constantly seeking to allow people the chance to live upon the island even if they can't help with the cause. It's a place he and his lone crewman spent many seasons working to build.

After all... The Captain set sail at a young age.