Marine vessel type

Hello, I need to make a bSDD URI mapping to a type of marine vessel.

Barge
A large flat-bottomed boat that is built for carrying goods and people on rivers and canals or in harbours, with or without sails, towed by a tug or horse. Also, a similar boat with its own engine.

It seems correct to define this as IfcVehicle.VEHICLEMARINE

How can I then distinguish it from a life raft or other vessel using the bSDD URI ?

Is that possible, or should I approach this differently?

http://ifc43-docs.standards.buildingsmart.org/IFC/RELEASE/IFC4x3/HTML/lexical/IfcVehicleTypeEnum.htm

Yes, you are correct: for more detail you either (a) use USERDEFINED and set the ElementType/ObjectType or (b) add property sets or classifications to make your specialisation.

Can you share more of your overall use-case, either here or nn@aec3.com