Im baffled by the fact that we all still tie shrimp/prawn flies the wrong way. I spent some time recently watching sand prawns after we pumped them from the holes and then looked around youtube. They only really swim backwards the second they leave burrow. After that they swim forwards, eventually digging back into a burrow front ways.
Fished these guys this weekend.... They dont look great out the water but in the water they look magnificent. They float for the first second or two and then sinks quite fast.