I wish that Olympus or Panasonic or Sigma would offer a nice fixed lens in the 9-11mm range.
As for this Laowa lens, perhaps if I already had one or more ports that I thought might work for it, and had been wishing for a wider fixed lens, and had the money and time to play with the idea, and was willing to experiment with fitting the lens to a port, and making or adapting a focus ring or settling for fixed focus, this could be an entertaining experiment.
Otherwise, I would use the existing Ply and Pana lenses, 8mm, 12mm, 7-14, 9-18, 12-40, 12-50, macro lenses, etc.
Overall, I am having some trouble figuring out how the Laowa would be preferable underwater to one of the 8mm FE lenses.
But that is just me. If it is appealing to you, go for it and then let us know how it works out!