Turn down your antialiasing to about 2x and mess around with that. See if it improves. There's a few guides online about increasing fps give them a try too.
Also depending on how good your PC is and if you record turn that off, that's what caused me shit frames and stuttering.
this thread is 3 years old...
but basically you go to the shipwreck that will be marked on the map with an excavator and press windows key, Works for everyone I've been too.