Empty tub, rub with a wet cloth and rubbing compound until the area is even. If you can't get the scratches out this way, go to 400, then 600 then 1200 grit wet/dry paper followed by the rubbing compound.
Then go over it lightly and quickly with a power buffer with the finest compound you can find.
Clean up the mess, put on a protective high-temp polish such as "Spa Shine" and fill and enjoy your spa.