Now thats something

The ancient serpent spirit obviously

squiggle boi that goes :v
or, the more common name, some type of moray eel.

But where are its organs? And what does it look like when it just ate?

As they are the larva of the eel they have very simple internal organs, their gut is a long tube in the centre of their body that is also transparent. They feed on really little particles (marine snow) so this food is digested through their gut but remains pretty much unseen as it is so tiny until they start metamorphosis into their adult forms where they start to show colour.