There is no "along them". Unless you can predict their velocity, and movement relative to the flight path
I have been able to predict the "along" of small swells sufficiently to land along the crest for practice, such that the landing was safe. Though that was only a foot or so swell, not the seemingly ten foot swells I have seen in the Pacific off Point Loma! It requires some judgement as to the small acute angle to be flown relative to the swell crest so the plane follows the crest as it moves. Those were short wavelength boat swells rather that longer wavelength open ocean swells I have seen, and fear! If I had to ditch in the open ocean, I sure would be trying to work out that acute angle to the swell crest, as slamming into the water (face of a swell at a near right angle) in an airplane is a much harder stop than it would seem! I have spent a lot of time looking down at ocean from the cockpit of a single, thinking how I would ditch it. In my flying boat, in mild conditions in the nearby lake, I can practice.