Needless to say once we dug into how it's usually done, we found yet another industry that's become horribly eco unfriendly.
Burn the body in a gas furnace for a few hours and release loads of ugly things. Including all the artificial fibres, coffin glues and plastics, and any fillings, implants etc. Mercury amalgam fillings can get to surrounding animals, even into fish off the coast. From memory something like 20% of uk atmospheric dioxins are from cremation.
If burying, the formaldehyde and other embalming chemicals leech into the ground along with any accumulated toxins in the body, and can prevent proper decomposition for decades or more. Embalming that's completely unnecessary for the timescale of most burials. Mostly those chemicals are ugly, and little studied when put in the ground in scale. Yet are studied when added in small amounts as fire retardants or glues in furniture etc. Then you have the US using steel coffins in concrete lined graves!
It's quite the ugly rabbit hole once you descend and start looking into burial and cremation.
Edit: maybe weigh it down. That would work. And by "it" I mean yourself, I guess.
I think the consensus was that it was suicides or other drowning victims, not some nefarious plot, but people get twitchy.