Who holds them
The Bailiff, at step 4, holds the way from Coastal Waters to the Broken Reef. The Actuary, at step 7, holds the way to the Abyss. The bestiary has what is known about them, and it is not much.
Breaking one
Kill it and you know the way for good, whatever later happens to the ship. That doesn't go down with anything. Your chart stops showing it, and something it had confiscated is yours for the taking.
A broken gate also opens a charted passage. A voyage can start at the water it opened, without the walk through waters you have outgrown. Home is as far as ever.
Running from one
The way is shut. It watches you back off, and makes a note, and you are put back a row. Come at it again and it will be waiting at full hull, with whatever it already took from you.
Slipping one
A Sloop that gets away from a gate at range goes through on the shoal side, where nothing with a keel should fit. It costs one more leg home, and a writ takes 50% of what she lands, for each gate she slipped. She can see the deep early. She can't get rich doing it.