Homebrew boats

[Itsallicanafford]

Quite a few of these type of boats floating around Copenhagen harbour this weekend, the chaps aboard were having a great time...anybody ever done anything similar?

Few whimsical questions as I have no intention of building one!:-

In the UK assume if you were to try this on a suitable stretch of water somebody official would stop play?

How have they built this, section of pontoon or similar form the hull?

[Simpo Two]

Well there were some strange contraptions at Ely Aquafest last year. I presume the EA turn a blind eye to licencing requirements because normally the moment a hull hits the water you have to pay them a few hundred quid.