Durabilities in Naval Action is a lot like lives for your ship, depening on the ship and how you got it it can either have 1, 2, 3, 4 or 5 durabilities, if all durabilities is lost you can say bye to the ship and any upgrades and modules you had on it, as a result you need to be stratigic with what you put on your low dura ships.

Durabilities are not replenishable!