I really don't think you'd need to worry about insta-death on touching/entering water.
If there won't be swimming, I'd imagine they'd go for the "invisible walls stop you from going into deep water" from Witcher 1 and 2 instead of "touching water = death".
As for whether there will be swimming... maybe it's my 2018 viewpoint (and I know a counter-argument for this was already made here), but I don't think going swimming with cyberware (metal and electricity) is a particularly smart idea. Especially if it's seawater (= salty).
But, as a mechanic I wouldn't mind swimming, if it does turn out technology in 2077 is advanced enough to not mind.