Yes you can. If you hold your breath in your chest and not your mouth, your body will float just fine. The more you panic and thrash around, the easier you'll sink.That's fascinating, I want to try this out. I always have a hard time treading water because I'm a weightlifter (so over 200 lbs but comparatively less body fat) and it feels like I sink quicker than my friends unless I tread water at a really quick pace, which burns me out.