Mine doesn't float at all. I'm not sure if it would even under full throttle. The only reason I stopped giving it the gas was that it was the more gas I gave it the more it was sinking into the sand. I did hop off of it but it wasn't going anywhere and that's when I reached for the winch line and it stalled. I'm sure I was sucking water into the engine from the exhaust while it was stalled. I didn't stand it up on end when I was cranking it with the plugs out and I'm sureIf you're ever in doubt, floor it until you're out. An atv may die out in deep water and when it does even with snorkles (unless you have mufler snorked too it will allow water to straight into the motor from the exhaust. So stay on the throttle, you said the front was up and the seat was up, if necessary dunno how much you weigh but get off and floor it so the front will be floating and your intake will be ok. Never let it idle in deep stuff.
Mine will float with me on it well at least the front will, the rear racks usually go under and the front comes up until half the front tire is out of the water and it floats.
Does your ATV actually float? We tried to see if my buddy's Honda foreman would float and had one of us on each wheel and it would've sank if we didn't hold on to it.