Board Thread:Warhammer 40k General Discussion/@comment-7499389-20130407223055/@comment-7186329-20130408184742

Space Marines Can swim.

The armour is a completely sealed enviorment, it can survive deep space and the ocean floor, easily whistanding the pressure. The power armour has air in it, it cannot sink because it floats on the same basis as a ship. It has enought air in it and displaces enought water to float, which would allow a marine to, at the least, dog paddle to shore.

Naval and underwater warfare has not been explored by GW because that would mean adding new IG companiew, equipment and battles to the 40k lore. As they are preocupied at the moment there simply is not enought time to add to it.

There is probably atleast one chapter out there specialising in underwater warfare. They would probably have a water proof version of the jetpack, very simple technology by Imperial standarts, and be deployed primarily to all water planets.

Can Space Marines do synchronized swimming? Nope.