IIRC, the original WH claim was that it was a 'muslim custom'.
Yeah, strangers zipping the guy up in a body bag and dumping it over the side of a ship is a muslim custom. Right (/s).
One thing that oddly sticks in my mind from an old 1950s nursing text that I read a long time ago had to do with Muslim burial custom. They like em planted within a day of death.
I still think there’s shenanigans, but I’m fairly sure that custom is the one being referred to. Not sure if burial at sea is considered equivalent. No real desire to look very much into Islam crap to find out, either...sorry.