The United States, who is not part of OPEC, with its recent discoveries in fracking and shale oil extraction, proved to be problematic for the clout. If oil supplies can be freely adjusted, OPEC would lose the grip on oil prices. There is only a small problem with shale oil: fracking costs significantly more than regular drilling.
And so, armed with this information, OPEC decided to massively increase production temporarily, so as to drop oil price low enough to squeeze American oil industry out of business.
On the other hand, the current decline in crude oil prices must have been a boon to the shipping industry. As bunker oil prices dropped, shippers are making fewer relatively short jaunts of common shipping routes. Instead we have more ships exploring longer, less standard, and potentially more lucrative trips.