WARNING: SOME READERS MAY BE DISTURBED BY THE CONTENT OF THIS ARTICLE.
According to a study[1]https://blogs.scientificamerican.com/news-blog/how-long-do-dead-bodies-remain-inta-2009-06-10/, in the journal Legal Medicine examined nine bodies that had drifted hundreds of kilometers in cold waters off the coast of Portugal and Spain. Bodies recovered in the first week were in good condition, but the beginning signs of decomposition were present on a body recovered after eight days. The two bodies recovered after 20 days were highly decomposed and could only be identified through DNA analysis or dental records. As for warmer water, A 2008 study on two human bodies recovered following aircraft accidents found one body off of Sicily to be partially skeletonized after 34 days and a second body off of Namibia to be completely skeletonized after three months.
According to BBC ScienceFocus[2]https://www.sciencefocus.com/the-human-body/how-long-does-it-take-for-a-body-to-decompose-at-sea/, It depends on the temperature of the water. Bodies have been retrieved almost completely intact from waters below 7°C after several weeks, and as recognisable skeletons after five years. In tropical waters such as the Arabian sea, it’s a different story. Even a weighted body will normally float to the surface after three or four days, exposing it to sea birds and buffeting from the waves. Putrefaction and scavenging creatures will dismember the corpse in a week or two and the bones will sink to the seabed. There they may be slowly buried by marine silt or broken down further over months or years, depending on the acidity of the water.