Queensland State Archives posted a photo:
Suction dredgers operate by sucking river or sea-bed material through a long tube, like some vacuum cleaners but on a larger scale.
A plain suction dredger has no tool at the end of the suction pipe to disturb the material. This is often the most commonly used form of dredging.
A bucket dredger is equipped with a bucket dredge, which is a device that picks up sediment by mechanical means, often with many circulating buckets attached to a wheel or chain.
Some bucket dredgers and grab dredgers are powerful enough to rip out coral to make a shipping channel through coral reefs.
Description source:
Wikipedia
View the original image at the Queensland State Archives:
Digital Image ID 12434