seems like lots of false starts in track, but hardly ever any false starts in swimming....

Why the difference?

Swimmers don't try to anticipate the start, runners do

tracks first false start is charged to the field. IN swimming, that rule was taken away a while back. If a swimmer false starts, they are out.

Yup you jump into the water prematurely you get to sit for a while and wonder.

A recent rule change on starts - that came to play out with the Chinese girl DQ'd in 100 free:

If the judges call a false start they can let the race go and DQ the swimmer after the swim. In the past they always called the heat back to the blocks. They made this rule change to NOT penalize the field which tends to become cautious after a false start.