Here in Japan signal flags are the norm.
What is this one?

Coming to get you ?

Close Planter.
I am towing a submerged object.
Around here that is usually aquaculture gear like fish breeding frames, oyster or scallop farms.

Failed that one in my license. That;s why I know now.

Interesting. Is this flag/kite peculiar to Japan? I tend to associate a red and white flag with indicating a pilot vessel.

Do they also show day shapes, such as a black diamond for towing with line more than 200 metres, and lights at night - 2 white lights for towing with line less than 200m and 3 white lights for more than 200m?

Not that I expect to be sailing in Japan anytime...

Looks like you are close to correct Quix.

Japan has specific national marine regulations for heavy traffic areas. These differ from international regs.
I posted that this flag was ,I am towing a submerged object. That's what it means in my area.
But in heavy traffic areas it is like an escort vehicle for wide loads on the road.
I actually means. There is a big bugger behind me and he has the right of way, no matter what you think.
I didn't know that and now I do.gary