Shares of United Maritime Corp. /zigman2/quotes/236697405/composite USEA +0.02% more than quadrupled in very volatile trading in their Nasdaq debut Wednesday, enough to lead all gainers on major U.S. exchanges. The seaborne transportation services company completed its spinoff from Greece-based marine dry bulk transportation services company Seanergy Maritime Holdings Corp. /zigman2/quotes/200900682/composite SHIP -1.54% on Tuesday, and the shares started trading as of Wednesday morning. They were up 310% in afternoon trading, and have been halted for volatility no less than five times so far. Seanergy's stock, minus its United Maritime subsidiary, slumped 11.9% to trade at an 18-month low. As part of the spinoff, Seanergy shareholders received one United Maritime share for each 118 Seanergy shares they held as of June 28. Seanergy's stock has tumbled 25.0% year to date, while the S&P 500 /zigman2/quotes/210599714/realtime SPX +0.80% has lost 19.6%.