I've seen them in blue water... But it's tough. Good vis, bait ball, and they were on the outside of it out of view except for quick flashes. Humpback whales bubble net salmon, and they seem to be spooked of bubbles from divers. Snorkeling may work.... I know of at least one spearfisherman who used to hunt them while freediving.
Another option is to find the streams and pools that they spawn in and shoot photos in freshwater, or the salt just outside it... That's the easiest way to get salmon pictures, and you'll have no shortage of subjects. Just be very careful not to disturb the redds. In some streams/pools that may be nearly impossible and best to stay in the brackish water or salt to avoid disrupting spawning activities.
GoPro on a weighted tripod works really well for salmon pictures.