I ~think~ FotRSU does it the same way... the <D> will send you down and down and down... till you either hit bottom, do <A> to level-off, or set a depth on the gauge. Otherwise the crew says: "Captain said dive, so we dive." The <Ctrl><D> will initiate the "Crash Dive!" and take your boat to the pre-set depth, which in the Balao is scary after you've been driving a Gato...