> Also what is a good % of body fat to have as a female swimmer?
This is a an optimization problem that has several competing interdependent
variables which cannot all assume their individual optimal values
simultaneously for a single given % body fat figure. A lot depends on your
priority of events (sprint, intermediate, etc.); your priority of strokes
(back, ***, etc.); the specific gravity of the medium you intend to swim in
(ultra-salty Dead Sea at negative altitude, distilled deuterium-depleted water
at 5000 meters altitude in Katmandu, etc.); the temperature of the medium
you intend to swim in (frigid English channel, Hot Springs Arkansas, etc.);
and your personal physical anthropological features (height, bone structure,
etc.) to name but a few.
Note also that it is not just the % of body mass accounted for by fat that is
of importance. The spatial distribution of that % fat is important if you are
concerned with speed, with mechanical insulation, or with sculpting a
hydrodynamically optimal body contour. The chemical distribution among
molecular structures of that % fat is important if you are concerned with
buoyancy, with thermal insulation, or with your long term health after
retiring from intensive swimming competition.
In any event I would trust the judgement of your team physician over any
numerical guesses from people on the net who don't know you personally and
don't know your specific short term and long term circumstances and objectives.