Not all that difficult on miniatures, but just a bit repetitve when making 16 of them.
The boat shells were made from 0.015 plasticard sheet vacuum formed in a small home-made vacuum box used in conjunction with a normal vacuum cleaner. The insides (seats/thwarts) are just flat images drawn in large scale and shrunk down on the computer, stuck on plasticard, cut out and stuck in the boats. The grablines were also made on the computer and stuck on.
The keels are fine copper wire glued on. Boats spray painted with white matt aerosol primer (Halfords) .
Works very well for miniatures, but would probably look a bit “phoney” on larger models!
All an illusion really!
Bob