On the flip side, Kroak is the most magical being that ever lived in the warhammer universe, greater than every other magic user combined, times 10. That goes double for things left underwater.
Reason for this is a rainforest/jungle environment to begin with, there is a huge amount of bacteria, fungus, and other things that quickly break down any remains left out in the open. In real life, I am 99% sure that the bodily remains of this magical priest would have rotted away a looooong time ago. Lord Kroak's mummified remains under water? As much as I loved the slann picture in the previous post, THIS is the picture that made me think the most.