Concrete is commonly used for structures that are partially or completely submerged, as its hydraulic qualities mean that in most cases it can be set underwater without much additional hassle.
This is something that has been known since Caesarea and the Roman Empire, and to this day so many bridges and docks rely on concrete as a construction material.
This leads to the question of whether concrete repairs are as easy and straightforward, and the answer is that they certainly can be, but there are different factors to keep in mind when making underwater concrete repairs compared to ones made on dry land.
The process of curing concrete does not require air to set, and in fact, concrete that sets underwater cures more completely than on the surface, and the outer casing that can be a weakness is a strength underwater as it protects the harder core whilst it cures completely.
Most concrete repair methods can be adapted to underwater use, although they have to obviously be mindful of the increased pressure that is found in aquatic conditions, and typically can only be completed using specialist products and experienced contractors skilled at working underwater.
Exactly which method is used depends on the level of damage, with small areas typically treated by installing jackets over the particular repair section to form a seal before pumping in a cement grout to fill up the area.
These jackets can be as simple as plywood covers or can be more complex waterproof textiles, depending on the type of job being undertaken.
For larger areas, pumped concrete using a tremie system is typically used instead to ensure that concrete reaches the damaged area and starts to cure in the right location, forming the outer shell that allows the rest of the structure to cure securely.
It is not a simple job, but it is far more possible with many more repair options than a lot of people expect.