I am taking either my Patek Nautilus, AP Royal Oak, VC Overseas, Breguet Marine or BB Aqualung. All of them have their merits.
But if real sport, in my case diving, is in the program, I am choosing one of many Rolex Submariners - those are very hard to beat. In some cases I might take Blancpain Fifty Fathoms or my GP Sea Hawk II in Ti with Ti bracelet. That is really a nice watch! I think this one has not received the appreciation it deserves.
Best, Kari