It is called a SWATH (Small Waterplane Area Twin Hull).

The problem is that they don't have as large a waterplane area as conventional vessels (refer the name) and therefore have less load carrying capacity. This basically means that they will sink, trim and heel more than a conventional vessel under the same loads.

Not a problem for vessels that have a very definite load and operating environment, infact they can perform their tasks very will if designed correctly. They are also fairly good seakeeping vessels if they have enough freeboard.

It is a problem however for sailing vessels that operate with large variations in trimming and heeling moments from the rigs.

The idea is correct though, you only have to worry about friction drag if completely submerged. SWATHS generally have lower wave drag than conventional vessels.

HSV 2 is not a true SWATH, but it has similar principles applied to its design.