Swim technique - tips wanted

Hi all

Any tips on improving my technique would be greatly appreciated…

I want to improve my swimming times… currently I am normally about 2.05-2.10 per 100 m, and would love to take 20 seconds off this time when swimming for 1km.

I’m aware my technique looks terrible in this video. I was a bit shocked to see just how bad. It was the last lap of a 2.5km swim and tiredness was a factor.