Alongside aquatic vehicles like aqua speeder and surface vehicle like Jumpers, Alliance soldiers have managed to domesticate indigenous slug-like arthropods as beasts of burden and mounts to help them navigate waters and grounds of their temporary home.
Then, the Empire came.
As soon as the orbiting blockade has been established, Imperials started the assault on various fronts all across the planet. Underwater TIE fighters engaged the Rebel underwater facilities, while ground troops led by new mammoth AT-HA walkers started bombardment of Alliance's surface facilities. The battles were extensive and grueling for all, but the Imperials were unpleasantly surprised by the Rebel's ingenuity and ferocity.
In the end, all of the Alliance survivors made their way from the planet with the help of friendly faces in their proud ships.