the.com/sandbank
A river's loose change, piled high enough to wreck your boat.
means A raised ridge of sand built up by currents in a sea or river, often a hidden hazard to ships.
from Plain Old English carpentry: sand plus banc, a ridge or bench — the riverbed's furniture, rearranged nightly by the tide.
Always movingCurrents reshape them constantly, foiling old sea charts.
Ship trapCountless wrecks ran aground on these soft ambushes.
New landSome grow into islands, sandbars turned real estate.