That's a difficult question, as there's no single correct answer. There are so many variables. Which ocean? Which part of that ocean? What time of the year? What time of the day? Under what weather conditions? What is the depth of the water at the point where you're looking at it?
The sea can appear different hues of blue:
For a brief time at sunrise, it can appear pink:
So when it comes to painting ship bases, you can choose the shade that appeals most strongly to you. Personally, I prefer a darker look:
Next I add a wake and the propellor wash:
Without getting into a heavyweight discussion of the physics of wave formation, I'll just say that the simple view of "the bigger the ship, the bigger the wake" is not always correct. The wake's size is a function of both the mass of the ship that's displacing the water and the rapidity with which the water is displaced. So, a destroyer high-stepping at 35 kts will have a more pronounced and more disturbed wake than will a battleship crawling along at 5 kts. However, because of the mass difference, a battleship at 25 kts will have a wake several times the size of the one produced by a destroyer at 35 kts. This is why I never became a physicist. Too much math!
That's a very wordy and roundabout way of saying wake sizes vary a lot for a variety of reasons, so I paint different sized ones according to my whim that day. Here's a base with a pronounced wake:
In reality, the disturbed areas of "white water" in a ship's wake will appear matte, as opposed to the gloss of the sea around it. After I paint on the white areas (any bright white will do) and blend them in at their edges, I go over all of the white with brush-on Vallejo Matte Varnish (520).
For me, doing the base is child's play compared to the intricate (and often infuriating) job of painting the ship that will occupy the base. Anyway, how do you do your bases?