From what I can see on their website Ocean's Depth/Black would be the closest color. And thanks for the question. I have been looking for navy in this style and this is a new color, I would not have looked otherwise.
The flip flop did not slide on my feet when wet. I got the water proof kind. I walked 20k+ steps a day and most of it was in Volcano Bay water park. Never slipped or had an issue. I did wear them around the house for 3 days to break in as well. I wear them every day. I’m obsessed!