So, obviously finding a metal shark was not on the things to do in the episode but it brought up a very valid point within the crew.
The bots actually were taught how to swim (by Cody, of course. No one else was going to do it), which meant learning how to try and keep themselves upon water and not let them fall down into rhe underwater abyss.
Now although all the bots are similar, the amount they have of metallic weight is very much different, and makes the teaching completely harder to do because of it due to much more needed effort.
Blades was pretty lightweight, but he just had an overall problem with being in the water from the amount of shows he has watched. He kept on yelling that he didn't want to die, even though he was reassured that nothing bad would happen.
Chase was a floating starfish, having caught on the whole thing with ease. He was just flat out in the water, but not fully at the surface of it, but it was definietly ease to spot him (no it was not).
Heatwave ran into problems, because his own weight varies depending on how much water is in his tanks. He can't go underwater with the tanks full because they could burst. Besdies that, he did well for swimming.
Boulder had trouble, but there is a ton of blame on his feet because they easily scoop water and mess up his practice. That didn't fully stop him though, and managed to do well in swimming.
But all of them can agree that saltwater sucks.