"There are parts of the ocean which are dead no oxygen in the water which means nothing can survive, no fish no plankton nothing at all. They are spreading exponentially. Whilst they are tiny now and have been. At the rate of growth. They’ll cause serious problems before the end of the century."
"The Mariana trench is deeper than Everest is tall."
Not a bad idea but you might want to avoid the word dumping.
Burial at sea is the more common term.
More likely than not the writer was referring to Hawley Harvey Crippen. Check out the article at www.thehistorypress.co.uk/articles/the-notorious-case-of-dr-crippen/