Out of 50 yrs making models I’ve never really done a Diorama, although this one moght be considered a vignette. I still need to add a small weather tower next to it as there was one attached to the sub that launched it. And some white for the ripples on the waves.
The mast you are referring to is called the test and instrumentation mast or T&I mast. It was attached to the boat when we did shots off the coast of Florida on the Atlantic missile test range.
My last duty station was at the Naval Ordnance Test Unit (NOTU) at Cape Canaveral and I was involved with several Trident 1 and 2 launches from both US boats and UK boats.
A great theme, very effective, very well done. It’s just water, a splash and a missile but it feels like you can look at it for so, so long and pull so much from it. And the splash looks so incredibly real. Great job!!