What is Secondary stability?

Secondary stability, also known as reserve stability, is a boat or ship's ability to right itself at large angles of heel , as opposed to primary or initial stability, the boat's tendency to stay laterally upright when tilted to low angles.

The study of initial and secondary stability are part of naval architecture as applied to small watercraft.

A greater lateral width and more initial stability decrease the secondary stability- once tilted more than a certain angle the boat is conversely harder to restore to its stable upright position.