Ridiculous D&D contrivances

[KazilDarkeye]

Yeah, but that still doesn't explain how the shark (or whatever, because it doesn't have to be a shark*) manages to SEE through the lava.
I can easily imagine see-through acid, but see-through lava?

* Any other good options here for creatures/liquids? Creatures are easy enough:
Piranha Swarm
Jellyfish Swarm
Barracuda
Electric Eel
Giant Crab
Stingray
Squid
<sigh...> Squark
Kraken (is that allowed?)

But are there any notable substances?
Sand maybe?
Powdered Glass?
Blood?
Crude Oil?
-Edit: Actually scratch that last one unless the creature gains fire resistance/immunity