I don't recall if the Wookie Catamaran was ever shown in the water, though the hull shape certainly leads one to believe that water landings were part of the plan. I think this image is more fan art than canon but you wouldn't be the first to see the water relationship.
I'm not totally sure if they are ever shown in the water in movies or games? They seem to always be flying about.
I always thought the Droidekka felt appropriately scary. It seemed to be the one enemy that the Jedi tended to run from rather than face.
Mandalorian gives droids a more threatening feel. Maybe that results from the "normal" vs. droid match up. That might not be so scary for a Jedi, but for the other 99.999% of the galaxy they would be pretty worthy adversaries. Even Mando has his struggles with the Security droids in the prison break episode. He clearly has a means to handle them, but they aren't pushovers and don't get treated as non-threatening. And of course, the Droid army killing Mando's parents are given an ominous feel too. That scene has more of a massacre feel to it than simply overrunning some defenses or besting a local militia.