Science

...between terrestrial and freshwater environments, for example, to disperse over land before reproducing in a different body of water. Some of those have a specialized exoskeleton that holds a persistent bubble of air against the body, called a plastron. It serves as a functional gill, exchanging metabolic CO₂ for O₂ dissolved in the surrounding water. These also have some environmental restrictions, like needing reasonably well oxygenated water, but I wonder whether such a species pre-adapted to both terrestrial and aquatic habitats might be a natural choice for this sort of thing.

In practice, well studied systems tend to become entrenched, so since manipulating the behavior of large large terrestrial cockroaches is already understood, those roaches are more likely to be re-adapted to aquatic systems instead of using an aquatic taxon to begin with.