at the very least, i think the greater pressure of water vs air affects construction workers negatively. then there's the difficulty of keeping repair materials from partly dissolving in water.

in that case a caisson can be used, if in an area that lends itself to such use.

but caissons come with potential difficulties such as failure and health problems for the workers.

https://www.researchgate.net/search.Search.html?type=project&query=caissons

https://worldwidescience.org/topicpages/c/caissons.html