Dwarves

I was just listening to "The Sword And The Chain". The dwarf said that he doesn't like boats because he would drown in 5 or 6 feet of water. This is due to higher muscle and bone density.

 

The DragonLance Dwarfs had a similar problem if I remember correctly, they could swim just not well or for very long, but they could hold their breath for a long time and walk along the bottom though. Is an issue for other types of Dwarfs in other stories as well.
Although there is also a species or two of D&D Sea and Amphibious Dwarfs as well, but not sure how well or how fast they could actively swim though but presumably they could, also Bucktoothed Dwarfs are a species of Dwarfen Beaverkin and their chaos changed cousins the Paradoxin(?) that a Dwarfen PlatypusKin.

 

Yes. I can see them being poor swimmers but able to hold their breath a long time, otherwise living underground would be next to impossible. I worked at a cave and know what happens if there’s a substantial amount of rain. A cavern(limestone anyway) will form along a fault Line or vertical joint in the ceiling letting water in which causes it to hollow everything out in the cavern. Water seeps in and brings with it calcite which forms stalagmites and stalactites (mites might reach the ceiling and tites hold tight) but anyway most caverns have pools of water and those pools fill up when it rains, sometimes it’s part of an aquifer and when it rains a lot becomes part of what is called an aquifer recharge, and the lower rooms fill up. Assuming a Dwarven kingdom is built along the bones of a cavern there’s bound to be water whenever they go deeper or farther not to mention when there’s a ton of rain. See it’s not like a flood where water violently enters the underground but a gradual rising from the floor until it fills the rooms. But who knows with Dwarven architecture maybe they have balanced everything to living under water and ways to stop nature from doing natural things. I can see them being able to swim some and hold breath longer, walking and working in chest level or higher water.

 

There's also the fact that they tend to prefer heavy weapons and armour, not good for swimming with.

 

They must have some weird lungs. Air circulation issues, mad air, lack of air. Furnaces underground can't be good for air either.

 

That’s why they get a boost to con and end.

 

Closing of the entrances that lead water into the tunnels and digging a system of drainage tunnels just in case would solve the flooding problem.