Cleaning fuel tank without removing

[McGillicuddy]

Fuel tank is drained and looks real clean. Can't get all fuel out (can see a small amount in aft end).

There are however some sand and small 1/8" gravel bits in there.

Is there a safe way to get these out (kind of hesitant to suck fuel fumes through a shop vac).

Any thoughts? Thanks.

McG