He colored up nicely. I would think he is able to swim fairly good. I had a girl that was literally missing her whole tail fin. It looked like someone cut it off
and she got around just fine. Luckily her tail did grow back fully. I have pics of her in my albums on here if you want to see her. Sadly, she died last year :(
There is also a member on here who has a female betta that has no tail. I don't think it was born with one. I forget the owners name though but I think the fish's name is tidbit or something like that.