The average depth of water around there is 12m or so, and the underwater part of the frigate is 3m in depth.
I love the Chinese fascination with figure and their total disregard of reality.
There are three basic things you will need to learn in order to stay off the rocks:
How to gauge the height of the tide and state of the current in your location
How to identify hazards on a chart
How to plot your position on a chart so you know where you are in relation to the hazards
First of those basics:
knowing how much water is under your boat.
Address chart symbols and plotting positions,
One also needs to be aware of water level and any possible currents in their areas. Where the water level is abnormally low is just as dangerous as a rock on a tidal coastline.
Most coastal locations on earth have two high-water and two low-water tides each day; these are referred to as diurnal tides.
The chief cause of tides is the gravitational effect of the moon and to a lesser extent that of the sun. Depths marked on charts are at "mean lower low water," which involves an average of the lower of the two daily lows.
The point is, the actual depth of water is the amount marked on the chart plus the height of tide at a given time. In extreme astronomical or weather conditions you should be aware there could be even less water than marked on the chart.
Depthsounders are helpful in telling you what is directly under you, but you should have an understanding of how your depthsounder is calibrated. Is depth being measured from the sounder's transducer or has it been adjusted to measure depth from the lowest point of the keel or prop? Know how your sounder is calibrated.
Depthsounders look down but they can't look ahead—so slow down in tight quarters.
(from my hard disk)