I never read through his full blog, but usually these things require a lot of planning! You can see by the drawing there's a lot of thought involved. It usually involves sculpting the waves using normal filler, having your models in place. Then you release your models out of the waves and make a mould from the waves into which you pour clear resin(adding blue or green to colour as you see fit. Once your diorama pieces are painted take out your waves and glue the whole thing together, filling any gaps with more resin.
But yes that is a great piece!!