I heard a different story. Apparently there was some one-time offer by the Feds in the 1930's to take liability for aircraft accidents on public waterways. For whatever short-sighted reason, Colorado didn't take advantage of the offer and has never wanted to allow it since.
That's what I heard, anyway. Haven't checked the validity. I think the Seaplane Pilots Assn. has the details in their book, if I remember correctly.
Received all of this from a pilot who refuses to join the Colorado Pilots Assn. because "they don't try to do anything about it". A discussion with CPA leadership at last year's Christmas party seemed to indicate that if a properly motivated person wanted to pursue it, CPA would support them, and it was likely to go nowhere.
With changes in the leadership at the Colorado Board of Aeronautics, the outcome is probably even more of a mystery. That was the commentary, and I'd add that with the State government budget weakness like many States right now, it's probably way down the list to create new rules, regulations, and licensing might have to be voted upon by the taxpayers due to TABOR.
I passed the info back to the complainant who immediately said he didn't have time and never spoke to me about CPA ever again.
Bottom line... If someone knows a State Senator who'd benefit significantly from a float-plane business in their district, it'll get done. Otherwise, it's a lost cause, IMHO.
Convince a politician or one of their family members or donators to open a fly fishing business on a river with fly-in access, and it'll be done in months.