Originally Posted by Jonson PL
Is it spray from the waves that created the mist ?
Yes, the waves. These long exposures are like a box of chocolates. You never know what you're going to get.

A story behind that shot was I was just going for a 2min exposure. During that time a sneaker wave came in and hit me up to my knees, soaked me inside my shoes and moved the tripod even though I held it. So I reset for a 1 min exposure so I could get out of there before it happen again. So after this sneaker wave, they didn't come in as far during that 60 seconds except for the last 10ish seconds a wave came in and consequently didn't get recorded much and gave that mist look.
If the waves would have came in steady and I did get the original 2min exposure, the waves may have looked like this taken the same day, same place, same rock but different angle. Note I report my ND filters by their density (9 stops X 0.3 = 2.7). And additional info for those other 67 shooters is I used a waist level finder and a one-degree, Pentax Spotmeter V.
Pentax 67, SMC Pentax 105mm ƒ2.4, ND2.7 filter, Fuji 100 Acros, PMK Pyro developer, 120 sec exposure