Pond people - what are these flies?

[SecondaryBurnzzz]

We have either incubated a swarm of weird mosquitos or they are water boatmen? or something else. The sit happily on the surface of the water.
There are loads of them - any ideas? And are they likely to stick around? As long as I know they aren't going to try to suck my blood I will like them more!

I've no idea what they are, but if they were going to try to suck your blood, they'd have done so by now.

They could just be trying to wear me down first?

I have googled them actually and they are flies. I'm rather proud of them now, just trying to work out what they're trying to tell me .

Ah, from your link - semaphore flies

S of England only - no wonder i haven't seen them. They look fun, and it says they eat midge larvae, so beneficial too.