For a unit to be able to swim, an addon, such as the CoC Diver, is needed.
Actually, I was playing a mission the other day......instead of continuing from my save from the day before.....I accidentally started from scratch.
So.....I thought to myself......nae bother.....I'll just eject from the chopper into the water and die.....then reload the mission and play from my save.
Except.....I didn't die......I waited and waited, meanwhile my men had reached land and disembarked and were wondering where I was.
So.....I started moving towards the land......1.5 Km away.
I made it to land, but by this time my men were all dead.
So, I ran around for a while......then I decided to try swimming back out to sea....I wanted to see if I would die this time.
I didn't die.....the funny thing is......I can make this happen with this mission almost every time.
I haven't tried to find out why yet, but I might sometime soon.
Planck