No Stupid Questions

Every multicellular creature lives in symbiosis with a plethora of bacteria, inside and outside of its system, those will always be the first to start decomposition. You'd need extreme conditions to sterilize those and avoid decomposition, and even then, there's pretty much not a cubic millimeter in the ocean that isn't filled with other bacteria and fungi.

Depends on the conditions, I'd say. If you have an area that has low oxygen and high saline concentration, one could potentially preserve large parts of the carcass. A big challenge though is the substances brought by the carcass itself, like enzymes and bacteria that are not directly exposed to the oxygen-deficient saline-abundant water, which can thrive and remain active for a long period of time. However, if this carcass sinks to incredible depths, where the pressure is really high, temperature is a constant 4 degrees, very low concentration of scavengers or thriving organisms, and potentially sinks a bit into the sediment for a long time, you'll essentially get ~~pickle juice~~ fossil fuel.

The sea is not "a salt brine in itself". You need a much higher salt concentration to pickle anything than what you find at any point in the ocean. Enough to prevent microbial life forms from surviving and consuming whatever it is you're trying to pickle, which is why it doesn't rot while pickling.

That wouldn't be very typickle.

Ehhh, the big factor is that a pickling brine is controlled and small.

You don't start out with an entire ecosystem of bacteria, fungi, scavengers, and the wide ranging temperatures that exist in an ocean.

Secondary to that, you tend to be dealing with cuts of meat when pickling, not entire bodies.

See, part of what causes decomposition are the enzymes released as individual cells die, and those produced by the bacteria already in the body.

When we slaughter an animal, it doesn't just get thrown in brine whole. If you did, it would rot from the inside, no matter what the outside brine was like.

Instead, the carcass is drained of blood, organs are removed, and the meat will typically be kept very cool during transport and storage. When you put that into the brine, you're severely limiting what bacteria are present in the first place. The brine will almost always be made with processed water from a tap, or from a known clean source like wells or springs. So, again, you have a very restricted range of bacteria.

The salt then limits them more. So you'll lack the bacteria that thrive in salty conditions in the ocean, and only those in the air and fresh water even have a chance to eat the meat before salt kills off the ones that won't ferment or otherwise preserve foods, including meats.

But! Deep sea conditions are very cold, and there has been footage of scavengers down there eating very well preserved carcasses. Some of that meat may well have pickled to some degree, as some of the fermentation bacteria can handle cold.

So, what it amounts to is that pickling isn't purely done by the action off salt on the food. Brine pickling is essentially sourdough for meats and veggies. You grow bacteria that prevent the food from going bad in a dangerous way, which leaves you with something that will stay edible much longer. That's kinda over simplified, but I think it's good enough for this

The ocean is absolutely PACKED with life like bacteria, viruses, and other microscopic organisms. Even if the salinity is high, it’s unlikely that you would get an ideal “pickling.” Hypothetically, if were there very few of those around for some reason, maybe? Maybe for a little bit. A more likely situation may be one where an organism was eventually fossilized due to being covered by something. And we ALL know being fossilized is better than being pickled, right?

If a dead thing would pickle, pretty much everything in the sea would end up pickled alive

I'm no expert in the field, but under the right conditions, possibly. But that would also be incredibly unlikely. The oceans are so full of life that something would feed on the remains, and even if not it would be more likely to decompose than be preserved. Bacteria is everywhere, including in the ocean, and bacteria is a significant component in decomposition.

I believe the brine solution we use for preserving food is a much higher salt concentration than sea water.

Idk, but dead whales become an entire ecosystem. They're called "whale fall" https://en.m.wikipedia.org/wiki/Whale_fall

out of curiosity what is the average salinity? We often use 0.85% saline to suspend organisms and red cells to keep osmotic pressure stable, I'm just curious if its around that level.

There are pockets and layers of water in the ocean that behave very differently from each other. There are areas of high salt concentration that pretty much act as death horizons for many organisms. There are waters completely devoid of oxygen that suffocate organisms that get lost or stuck in it.

So, in a sense: yes. However the degree to which marine life had adapted to these conditions, the more unlikely parameter is a dead organism not being consumed by scavengers.

Maybe in a brine pool but in most parts of the ocean the salt is not concentrated enough

Isn't that just what a fossil is? If you get a little creative about how you define pickling?