Imush Dirtclods needed to train swimming. Here's that moment where what is mechanically sound in terms of gameplay and what is narratively sound in terms on role play overlap. Novice swimmer generally needs to be trained to adequate swimmer to limit floundering/drowning in varying current or when falling 1 z-lvl into water.
Imush was lingering on the surface near his home fortress Craftsmassive so he's not had the chance. He fast traveled 5 world map tiles east and 2 north on the surface to the fortress Torchlash. While on his way down to the Torchlash warehouse to see if he could pick up an iron cap or helm, he stopped off in cavern level 1 to get that swimming in.
When it comes to training I prefer limiting the exercise as stat growth happens too quickly that way. Upon reach competent swimmer, endurance will advance from average to above average while under drowning status. Without drowning status, there is no change to endurance when competent swimmer is reached. As mentioned in a previous post, 1/5 of the way after competent swimmer, toughness will advance from above average to high while under drowning status. I don't want to say it's completely inorganic, but this can occur under more natural circumstances. If you kill enough critters, everything moves up. To me at least, it's about letting the game unfold and harvesting what's there as your character moves along.
Imush had sneak/ambusher on in cavern level 1 to make all those vision fields (cone, EXTRAVISION) visible. This way he keeps an eye out for giant cave spiders and is be able to locate critters he might not notice. Like pond grabbers whose blue p blends in completely with the blue 7 flow amounts in these underground waterways. Pond grabbers are harmless, but given dwarven tastes, good for meat, and good for advancing wrestling from dabbling to novice. It's also a natural way to briefly come in contact with that drowning status when passing by trees is unavoidable, as you often need to make your way to those pond grabbers or give chase. That's what's in season. Directly swimming under a bridge to reap the benefit of drowning is like flying in non-seasonal produce. Everyone's mileage varies on that of course.