I used acrylic paint, ink and charcoal here on a heavy acrylic paper. The colours are not strictly true to life but I love this combination of blue and brown and I think the two together look exactly how the sea smells, if that makes any sense at all..
The paint is thicker here in places. These sketches are still wet as I photographed them. They were done in one sitting - I might have a look at them again when the paint is dry and make some additions. Here's one below of the Heron. It is done on a light weight coloured paper.
I will add some chalk or white pastel to this one when it is dry just where the rocks have bled in to the sea on the top half of the sketch.