The main thing is how little is growing on it, since that makes invariably wrecks look unrecognisable, and usually hastens their degradation

(the Titanic isn't spectacularly rusting because it's sat in water with very low oxygen contect, it's spectacularly rusting because there's a microbe feeding on it. The well preserved wooden wrecks tend to be submerged in mud or in zones with relatively little life too)

Maybe the initial picture most of us have regarding ship wrecks is ships built from metal, which rust and fall apart significantly easier when submerged.