Fish are streamlined for propulsion.
Their bodies create little friction between them and the water that supports them. Light filters down from the water’s surface where we watch them take graceful turns around their aquarium tank’s curves.
In another aquarium, jelly fish, who aren’t moving like the fish, have dangling tentacles shown off with back lighting.
The jelly fish are almost transparent, catching food in their tentacles and letting themselves be propelled by currents or by ingesting water and spitting it out to move in the direction of their prey.
They are other worldly.
Floating with ocean currents is smarter than fighting them.
Personally, I watch for tentacles, both in the water, and out, all the time.
Jellyfish aren’t the only organisms on this planet that have a sting.