Shares of DryShips Inc. rocketed 26% in active premarket trade Thursday, after the cargo ship operator said it received a buyout proposal from SPII Holdings Inc., which is controlled by DryShips' Chairman and Chief Executive George Economou. Trading volume topped 360,000 shares ahead of the open, already more than the full-day average of about 303,000 shares. Greece-based DryShips said its board of directors has formed a special committee of "disinterested directors" to consider the proposal. AS of Wednesday's stock closing price, DryShips had a market capitalization of $274.6 million, according to FactSet. DryShips' stock has dropped 29.9% over the past 12 months while the S&P 500 has gained 3.8%.