Edited to add 8 more photos. including a track from the poop and the rabbit carcass. Something pooped (and big!) on my porch off the dining room. In a City, but close to forested area/pond. We have no bears here. Too large for a cat I would think plus not their MO. Nothing on the porch to attract an animal, either--no food detritus.

Unfortunately this is deceased, sorry for the pictures :,(

I asked Scripps Institution of Oceanography at UC San Diego, here is their response:

Thanks for sending this over. We asked one of our experts here at Scripps and here is what he had to say regarding the images you sent:

It is indeed a California Moray Eel, Gymnothorax mordax. They are a fairly common local rocky reef and kelp forest resident here in Southern California. They wash up on beaches fairly regularly. Why do they wash up? It may be that their thick, leathery skin and tough muscle make them difficult for scavengers to pick apart and they eventually wash up. Even once they are on the beach, scavengers have a hard time getting in and tend to focus on the head and tail first. They also tend to bloat and skin retracts from their face, giving them a more terrifying visage than in life.