Saw an answer to this question one time.
They said it depends on the length and location of the cruise.
IE: If you are booked on a 100 day world cruise and you die part way thru . They keep the body refrigerated until the cruise is over. This eliminates a lot of paperwork for the cruise line and family member traveling with them.
SS Ithaca , Volendam , Mariner of the Seas (x2) , Veendam , Coral Princess , Island Princess (x3) , Emerald Princess,Sapphire Sapphire (x3),Diamond Princess