As mentioned earlier, there is also the possibility that the JMC was overtaking the tanker way too close due to the traffic, and way too fast.
As the JMC passes the tanker’s bow the high pressure causes her to sheer to starboard.
Being on manual helm the QM applies port helm as she is still passing, maybe at some speed.
But as she starts to draw ahead the force disappears but she is still carrying port helm, and the high pressure from the tanker starts to act on the midships.
Bring the much smaller vessel she is most affected as not having the bulk and mass of the larger,
The waters there are about 20/25 metres deep, and have Ramunia Shoals to the W msking it a shallow water situation, magnifying the effect.
She was darkened but there was probably nothing the tanker could have done once she started the overtake.
Also, in Singapore Strait there are strong tidal streams, which add to the hydrodynamics.
There is also, for want of a better term, a king of jet wash effect from other vessels in the ame lane ofr traffic flow.
I have been Master of 20,000 tonne MPPs trading in and out of Singapore to SE Asia. There have been numerous occasions, particularly with Panamax and now post Panamax vessels, creating large areas on turbulence and instability in their wake.
The first time it happened we were half a mile behind two box boats that had overtaken us and nearly all authority of the rudder was lost. We had to go to manual and slow down, the vessel was yawing +/- 15 degrees till we got out of the wake. I believe that this is an area of fluid dynamics that warrants further investigation.
The Colregs were written in a much simpler time for ship on ship situations, not the comples scenarios we seen in Singapore and the Yellow Sea, and one questions whether they need revision or are fit for purpose.
We, as an industry, have been getting away with this for a couple of decades. Singapore used to have almost a collision a month, same in Malacca, but as the VTS has improved this has lessened.
What I fear is what happens when the big one comes along.