This is a carp breaching for the second time over about three feet of water late October 2018. What's interesting about it is on this lake, that's all I have ever seen them do, I honestly don't think I have ever seen them roll. Rolling usual occurs over deeper water than this and the reason is because when a carp rolls what it is doing, is taking in a gulp of air. This gulp of air is absorbed and used to balance their swim bladder so they can go down deeper. Often just after a roll you will see a stream of bubbles hit the surface, this is excess air being expelled via the gills. So in this lake at the moment with depths of 3-4 feet rolling isn't required.
So why are they breaching? In the spring you will see a lot of this activity on a lake, far more than usual and this is because they are going through there cleaning rituals (see> https://thecarpcatcher.co.uk/thecarpcatchers_blog.php?post=168). After flashing on the bottom or against tree roots etc to dislodge parasites (typically Argulus) they will then often breach to shake or knock off the dislodged parasite. But this is late October and not early spring so if that's not happening what is?
I've been up trees following carp and have often seen them do this and for no apparent reason and so given that I'm only left with theories at this time. However, given my experiences over the years and drawing conclusions from various other animals and species it's clear to me that this is most likely just normal activity that they undertake to keep in condition. Like a cat washing itself or a dog scratching it's instinctive behaviour but also I think it has another use. I've noticed it's often the same carp doing this and often in the same place. Sometimes I have also noticed that it's a precursor to carp moving into an area and this leads me to the conclusion that it's probably also used as a form of communication. The reason fish group together is that there is safety in numbers, if the fish on the lake are not grouped together then I believe this is a way of achieving that. A clear signal to the carp in the vicinity that this is where we are going.