A second attempt with some refinements, most notably, to increase the Fresnel property of both Reflection and Transparency of the shader to almost 100 - it gives a much more realistic colouring. Also increased the Reflection to about 90% or more - some recent "research" i.e. being at the coast revealed how reflective seawater is.

Had to play around with the Roughness and Offset terrain settings quite a bit, but I'm quite pleased with the result.

Also, the boat was too large and wrongly placed - it now looks correctly scaled.

Does anyone know how to attach a scene to a post, as they get rejected as "unknown file extension" or something like that.

R