just browsing the internet today, and i came across this site.
awhile back there was a thread about "hovering".
this little sim demonstrates the trim and drain systems of a submarine,
and was made by a subsim member, or wpl member, XabbaRus.
test your hovering abilities by draining and triming the ballast and trim tanks .
i got the sub straight and level at 90 feet.
it would have stayed there forever once it was trimmed.
http://sub-log.com/buoyancy