Xiangyuan Pool: The S9’s First Day in a Lane Pool

Two hundred and ten minutes in a lane pool with a stopwatch is not a dive and does not pretend to be one. It is a test, and it exists because a rated runtime on a specification sheet tells you almost nothing about your machine in your conditions. The number we wanted was simple: how long does this S9 deliver a comfortable breath to a diver working at three metres, from full charge, before delivery noticeably drops.

How the test was run

Full charge overnight, then continuous running with a diver in the water working at a moderate pace — swimming lanes, not hovering — and a breath check every fifteen minutes against a reference we established at the start. Two divers alternating so nobody got cold, and a written record of pressure feel, motor note and battery indicator at each interval. The output was not a single number but a curve: the point at which delivery first felt different, and the point at which it became a problem.

What the numbers said

Delivery began to feel marginally different at around the three-hour mark and became noticeably harder at three and a half, which is inside the rated three and a half to six hours at the bottom of the range — and this was a machine working at three metres, which is easier than the depth it is rated for. The lesson is not that the rating is wrong; it is that a diver working hard in warm water draws more air than a test load, and that the honest planning number for a working day is the bottom of the range rather than the top. We now plan S9 dives at four hours and stop being surprised.

Why this is worth a day

Because it converts a specification into a personal number, and it does it once for the life of the machine. Every subsequent dive is planned against three and a half hours rather than against an optimistic ceiling, the dive day is designed around it, and nobody has to discover the limit in the water at the far end of a site. It also produced a useful side effect: the machine’s normal note is now something all four of us know, which means a change in that note on a real dive is immediately obvious.

What we would do differently

• Run the test again at six months and compare the curve, not the headline number
• Record motor note as well as delivery feel. It changes before delivery does
• Plan working dives at the bottom of the rated range, not the top
• Do this before the first real trip with any new machine. One day buys years of accurate planning