Have you ever been paddleboarding? It's so relaxing!
I sure do! me and my buddies can paddlers can stroke for hours and we often have races is only, But its only for well-trained watermen.
When was the first paddleboard created?
Well traditionally it was called prone or kneeling paddleboarding, So it must have been around 16th last century by my knowledge. 
How large is a traditional paddleboard?
Well they are about the size of a canoe but usually no larger, But they can vary in size depending on how many people it accommodates. 
I've only used my 1-man paddleboard.  How many does the largest one hold?
Im not sure actually, I know that one man boards, you can usually stand up and paddle surf which seems like a lot of fun.