Lloyd's List reports that "there are now 129 tankers deployed for temporary storage by traders and investment banks".

These oil hoarders continue to buy lower-priced oil now with the intention to sell it in the future at the currently higher oil prices in the futures market. (ie. trading the oil price contango)

The longer oil prices are in contango, and tanker rates remain low, the more traders will get into this trade. For those who can do it, it's pretty easy money.