Such big fluctuations are typical of dry bulk shipping markets in which small numbers of excess idle ships or small shortages of vessels can send market rates sharply down or up.
Howard Bright, head of dry cargo at Braemar Seascope, the London-based shipbrokers, put the sudden fall down partly to concerns about world economic health and, hence, demand for the commodities shipped in dry bulk ships.
"We've now come to the conclusion that none of us is immune from what has been going on in the States and the financial problems going on there," he said.
He also pointed to Brazilian iron ore exporters' efforts to win higher prices from Chinese steel mills, which has led to a drying-up of cargoes on the normally busy China-Brazil route.
The China Iron and Steel Association yesterday said Chinese steelmakers would not buy ore from Vale of Brazil in the short term in protest at the miner's attempt to raise its prices in the middle of the annual contracts.
Ships lying idle off Brazil were willing to accept almost any price for a new charter, Mr Bright said.
Philippe Van den Abeele, of Castalia, the shipping hedge fund, said there were empty ships everywhere.