I have a few ideas,
1) an axe bow, as commonly seen on Offshore supply vessels
2) clipper hull variants ie, hollow, flatbed,... (for making things like semi-subs)
3) this might be beyond the scope of the pack but something like a Jack up vessel
4) Moss-Rosenberg tanks
I know this might be asking a lot but the models for all the things except the jack-up seem relatively simple