Being a commercial diver, I believe they would be using the equivalent of a small gold dredge or water lift if you will. If you have a semi trash pump and know your way around PVC fittings you could make one. Being that your water depth is shallow you could operate it and never get your head underwater.
This is a 4" model it takes around 355 GPM. Scale it down to a 2" model and it will only require 55 GPM.
You can then just make a box near shore that can be excavated and let the waste material dump into there. It will then drain water back into your pond. For your application and pond size I feel a 2" would serve you best 3" max for price and efficiency.
If you wish to know more let me know, I don't always get on here regularly. The whole concept works off the Venturi Principle. Not sure If I am allowed to link youtube videos in posts so until I can double check posting rules I will hold off on that.
Hope this helps.
