Totally fine with swimming but sea combat is another thing entirely something I'm trying to get the devs to believe is a good idea.
i think we should aim for this is a pos launch addon where maybe sea combat will be a main thing for example on a new planet where is monstly water and maybe flying islands like in the fulgrim book ^^
if I see a space marine swimming I'm going back to wow, I'm telling you right now. power armour is a lot of things - buoyant is not one of them.
water should be traversable but this should slow your movement substantially. but no swimming just waist deep waters. oceans should not be ingame or have an affect in the game. rivers of lava should do damage.
I think having variable maps where things change over time is a great idea, if you think about the beach assault you could do, or not! dependant on the situation etc. Just changes things up a bit, and keeps the environment fresh, the sea could uncover all sorts of battlegrounds / sunken ships / rocks etc, for a few hours, that then simply disappear as the tide comes in... Changes in tactics would be needed and would change up the combat, instead of balls of people firing down corridors at each other, oh look something in the map has changed, now we can do this!... I don't think its too hard to do this? is it? make a battleground on the beach, set the tide to a timer... anyone trapped in water gets killed if it gets too deep. eh.. maybe hard,
I mean untill boats are available but for launch it would just take up unneeded space that could be used more wisely. But most characters wouldn't be able to swim for lore sake.
Well, a space marine would less "swim" and more "walk on the bottom while using the suit's internal oxygen recycler". Though that might be rather awkward without their helmet on unless there's a mouthpiece in the collar.