Lucky run...

Lucky is in the equation for this one, to break this record will need to destroy 2 SAM's while on the boat and have some lucky for the other 2 kill themselves earlier.

Possible alternative strategy:

I was able in one past run kill 3 SAM's with the M82, sniping them from the little hill in front of the boat at crash site. But the last one in the far right corner wasn't possible due AI never looking at my direction and M82 incapable of making damage to the SAM. It is possible to kill 2 while in the boat and the other most close to you with the M82 sniping the operators. Will be hard to pull off, but will save almost 10 seconds.