I love swimming in fresh or salt water in the summer.
I love to swim too! I usually do in a pool, but will be swimming in the ocean this weekend, Florida bound!
That sounds exciting! How long can you hold your breath underwater?
Not very long! I don't really like to go underwater too much, it burns my contacts. 
Oh I see. I love swimming since its a “low-impact” activity compared to land activities such as running, especially since I have a bad knee
Yes, I can understand that. Plus, it's a fun family activity too. Splashing and laughing!
yes you must be careful though, buoyancy varies on the basis of both body composition and this may cause some people to not swim well!