Explosive jellyfish

Question

Could a creature like this exist?

Jellyfish or cephalopod-like creatures that live in 'swarms' underwater. They float aimlessly around in a net formation. When one member detects prey below the formation they send a signal to the rest of the swarm.

A single member is 'elected' to be sacrificed in hunting. This member begins electrolosis, storing oxygen and hydrogen in lung-like sacks. It's body contracts, causing it to sink, leaving the formation where it is replaced. It continues to sink to the same depth or nearby to prey where it generates a spark, igniting the hydrogen and oxygen. The detonation causes a shockwave that kills the prey which floats into the swarm net above where it is consumed.

The swarm is protected by an outer ring of individuals that create fiery bursts to ward off predators.

Answer 1

Surprisingly Maybe?

https://en.wikipedia.org/wiki/Camponotus_saundersi there is a species of ant that does something similar in defense of the hive so the behaviour is not unheard off. Though your jelly fish would actually be very different from most jelly fish we know of, a superficial similarity would not be impossible.

The mechanism of explosion however is definitely wrong. Electrolysising water dramatically reduces its density and it would take massive pressures to counteract this (pressures that would themselves detonate the mixture) so your jelly fish would FLOAT before exploding not sink. In addition the energy requirements of electrolysising that much water mean your jelly fish ALREADY has enough energy to explode if it carries its own oxidiser. That being said there are other ways your jelly fish can explode, if it carries two hypergolic fuels for instance or if it just rapidly heats itself up or if it has a sack of natural explosive somewhere on its body. This is something that needs re-working but is not a deal-breaker.

Killing prey by shockwave is also very realistic I mean https://en.wikipedia.org/wiki/Blast_fishing humans do it but will mean your jelly fish need a very efficient reproductive system and/or massive specialisation to make it worth the loss.

Answer 2

Although it's definitely not impossible for a self sacrificing jellyfish to exist, I would simplify this a lot.

First, instead of a swarm I would have a single queen jelly, or maybe several, who create smaller jellies that will explode. Like a queen bee and worker drones. This way a large queen can eat prey that is bigger than the exploding jellies, while only needing a small amount of energy to make any individual drone jelly.

Secondly, I do not believe that jellies have enough muscle mass to contract gasses to a small enough space to sink. I would have these jellies be deep dwellers. The natural pressure compresses the gasses. The jellies offset the lift of the gasses with small calcium deposits inside their bodies. They attach prey above them by swimming up and letting their gas expand, causing them to float up into the prey. Then the prey sinks down to the queen jelly along with the drone's remains, which will contribute to a new drone.

A sparking organ is fine, a one time spark made from a chemical reaction could probably be made by a jelly, given it could evolve this feature at all. However, electrolysis seems unlikely. Instead, in needs only be impregnated with a small amount of gas when it is born. Possibly methane from digested preys the queen has consumed.

So yeah, colony of exploding jellyfish seems cool. (As a note, since the drone jellies use an electricity generating organ, so could the queen. It could locate prey the same way platypus do, and signal drones with certain currents of electricity.)