Maybe a commercial alloy grade step ladder could be rearranged. A nice wood platform at water . Hinged to legs of steps with big dia alloy pipe segments running pivot for snug pipe shaft secured to bottom of legs. Bolts better than welding ?? Maybe don't need platform at top but could be same.Would need some kind of bracing anyway to take outside weight. But it's narrower at the top The usual wire supports and padding. Just a thought.