The International Energy Agency predicts production to outstrip demand by a record 4 million barrels per day by next year. Meanwhile, there are about a billion barrels in tankers currently at sea.

New vessel orders were down more than 50% in the first half of this year, compared to the first half last year according to Clarksons, a ship brokerage.

Shadow fleets, groups of tanker ships used by sanctioned nations like Iran and Russia to move oil, comprise an estimated 17% of all international tankers, according to an Allianz report.

The cost to ship fuel has more than doubled since February.

Observers worry that the ship — a “pawn” in Yemen’s civil war — could spill its oil and affect fisheries and drinking water.

A string of recent oil tanker attacks is leading the industry to take extra precautions and raise shipping and insurance rates.