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.

They only recently made it mandatory for three visa types, but since introduced in October 2016, it’s always been an optional field when applying for an ESTA.

Edit:
Not that not providing your social media handle will benefit you, of course.