I greased a glass surface (ideal for its smoothmess) with kitchen oil and rolled a lump of mastic. I then made the keel while pressing the mastic with a square metal sheet until I got a perfectly triangular  shape. Then I waited for the MS to be dry enough to be manipulated without taking the risk of destroying its shape -but still bendable enough so that it would be take the curved shape while I would press it against the plaster form.

I followed the same technique to make the individual planks : a fine layer of Magic Sculp that i flattened between two sheets of greesed glass. Once the MS was dry enough, I took a ruler and cut out some planks that I pressed against the plaster form.

Note that a thicker lump was applied at the middle of the shape as it was needed. Of course as the MS was greased, I had no trouble in unmoulding the whole shape -though individual planks tended to fall apart later.

So well, here i had a pretty much dreadful result of course -though I tried with a small metal ruler to get the planking the straightest possible, some of the planks were of various thickness as the pictures show. So I had a hard time sanding the whole, and cutting the excesses with a small saw.

When I saw I couldn't do any better, I applied huge layers of tamiya filler and sanded the whole so that only bits of planking would appear -and also to guarantee that I would indeed get a perfect shape.

Once I was finished, I set up doing the inside of the boat. Once more the help of that excellent Conway book proved very valuable indeed. I found out that beneath the front of Elcoes you would normally find a small warehouse as well as sink and toilets. I am not very fond of toilet humor so I leave to somebody else the care of imagining some toilets hanging from a thread in the wreck. And I choose to model only the general inner structure of the boat knowing that anyway, nobody would notice anything as most of the parts would be hardly above half an inch from the water.
Using various length of evergreen, and helped form the pictures in my book I reproduced the rather intricate inner details. But then I had hard time to glue the plastic on my Magic Sculp planks (especially the V shaped shapes), In the end I just happened to have drown the whole in superglue, later using Tamiya filler as well as extra Magic Sculp to make the joints between overlapping bits of plastic to disappear.

All in all a very messy job, but it's funny how the fact that very few will be visible in the end tends to help getting such results

The plaster sea

Then I had to take care of the sea straight away. Let's be clear, I would normally end up every building part, every figure sculpting before switching to paint, leaving the sea for the last minute. But then I had an issue with that special bit of sea. Indeed I wanted to create a reasonably agitated sea so that the tip of the waves would sort of echo the triangular shape of the wreck -something that just forbid me to just pour some resin layer and then try to raise it with a tool. No, I needed to mould that sea in the same way I did in a number of former dioramas. But then there was some special problem with jaws, indeed the shape of the hull would leave quite a bit of it under the sea in such a way that at first I couldn't see how I would either retrieve the shape of the boat from the sea, or how I would place it again if I used some kind of dummy. But then I found a way doing that.
First I did the mould itself which was rather easy