"The Mauna Kea Volcano in Hawaii is the both the tallest Undersea mountain and the tallest volcano Hawaii. It sits 6000 meters below the surface of the ocean and stands a staggering 4000m above. Giving it an overall height from ocean floor to peak of 10,000m."
"Depending on the person then this could be scary or really cool.
Oceans can have underwater oceans, rivers and waterfalls. Due to different water temperatures and density and all that scientific nonsense."
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/