The most reliable early sign of seawall failure is not on the seawall. It is a depression in the yard six feet behind it.
A seawall does two jobs: it holds back water, and it holds back soil. The second job fails first, and it fails quietly. Material migrates out through joints, cracks and gaps below the waterline, and the space it leaves behind shows up as settlement on the land side long before the wall itself looks alarming.
That is why the catalogue below is organised by where you are standing rather than by severity. Once you can name what you are looking at, the next question is what it implies about scope — whether it is a repair or a replacement — and the honest answer for most of these signs is that it depends on what is happening at the toe, which is what an inspection is for. Every sign below reads the same way on a bulkhead, which in Florida usage is the same structure under a different name.
This page is the catalogue. When you have narrowed it to one thing, the failure library takes each symptom individually — likely cause, how urgent it is and why, whether the mechanism is usually repairable, the repairs that address it, when replacement becomes the likely answer, and the list an inspector has to work through before anybody can put a number on it.
Storm damage reads differently
Post-storm damage is not simply accelerated wear. Overtopping loads a wall from the wrong direction — water arrives on the land side and then has to leave, often taking fill with it. Documented evidence from Tampa Bay in 2024 shows this is not evenly distributed: on one barrier island the bay-side seawall was overtopped roughly twice as deeply as the Gulf-side one.