Sand only flys when it's windy,.. which means it's a good day for a windsurf.
You can't have it both ways. Sand flys and sailing,. or no sand flys and no saiing.

Or did you mean sand FLIES?

Because they are around when it's not windy and they are rotten little things.

Actually, the worst ones are up around the beaches at Lakeside in Cape Range National Park.
There's some great reefs to snorkel around near there and when you come out of the water, the little sods land on you and bite you like crazy.
A week or two later, wherever you were bitten, you come out in red pimples like chicken pox, and it's really itchy.

For some reason they don't bite until after you get wet.