I believe most use cases where really shallow draft is required has been taken over by waterjets. Less efficient than propellers, particularly at slow speed, bu

I believe most use cases where really shallow draft is required has been taken over by waterjets. Less efficient than propellers, particularly at slow speed, but more efficient than paddle wheels, AFAIU. Then there's other things like channels having been dredged over the years, roads have been massively improved, ships have echo sounders etc., so maybe there's less need nowadays for traversing really shallow waters with big boats.