Re: Professionals built the titanic...
An amateur also built (and crewed) the Teignmouth Electron. It did not end well.
Edited to add - I tried to find a link to the amateur who wanted to sail around Britain, and spent three days circumnavigating the Isle of Sheppey before he was rescued. Anyone?
My point is, not all amateurs are at the same skill level. Rather like professionals, really.