I've seen Short-finned Eels (the common ones in the rivers and lakes of south eastern Australia) 'swim' up to about 10m through mud which was firm enough for me to walk on. I'd try to catch them from puddles in drying lakes and billabongs, they'd bury into the mud and pop their heads out some time later, quite a distance from the puddle, sometimes pushing up from underneath large chunks of solidified mud. When the puddles dry out even more you'd just see their heads poking out into the air from the almost dried mud. Those things slither their way across incredible distances of dry land, it's amazing to think that they breed out in the ocean but still manage to exist in large numbers in some bodies of water you'd think are completely inaccessable to them. No wonder they're brilliant escape artists! I tried keeping them about 15 years ago. I actually did manage to contain them in the aquaria, but for some reason I had a lot of trouble keeping them alive. It used to astonish me that a creature which could live in filthy, stinking, firm mud in the hot sun would drop dead in a fish tank.
