Seashore Time (part 1)

Today I started a new panoramic painting. It is quite a lot larger than those I've done over the last 3 months or so and I'm looking forward to seeing how it pans out. The canvas is 900 x 600 mm (about 3 feet x 2 feet).

Obviously from the title of this post you get an idea of the theme. Note that the pinky colour etc. in the picture below is not acutally on the canvas, it's just a facet of the phone camera etc. that I used.This is still just pencil on white canvas at the moment.

This part of Seashore Time is incomplete. It takes up about a 9th of the canvas.

Given that hint (of the title), can you work out what this is yet?