I don't know if this will help, but if you Google "transparent boats", or "clear boat", there are many of them available, fairly cheaply, though I'm not sure any are in your size - most are 1 or 2 person "kayaks" or canoes. You could try to tie together several like a catamaran or trimaran, which people often casually do using paddles with kayaks and canoes in small groups, but the result for tourists would have to be structurally sound in moderate seas.
Remember, you are running it as a tourist boat, so provable (certified??) reasonable safety standards may be needed, more so than for individual private boaters, who can mostly do what they want. You could be sued or held criminally liable if something happened. Also, I wonder how safe that would be, if someone fell overboard.
(BTW, many people have made their own transparent kayaks and canoes, out of many materials (even transparent urethane, as strange as that sounds.) Without certification.
Many
imported (not U.S. made) transparent boats are at
Try A Wholesale Transparent Boat And Experience Luxury - Alibaba.com https://www.alibaba.com/showroom/transparent-boat.html.
E.g.,
Transparent Boat Clear Boat Clear Bottom Boat With Engine And Canopy - Buy Transparent Boat,Clear Boat,Boat With Engine Product on Alibaba.com https://www.alibaba.com/product-detail/Transparent-Boat-Clear-Boat-Clear-Bottom_1600942388020.html?spm=a2700.7724857.0.0.28261fc5xjffUk
Sunlife Best Seller Transparent Clear Boat For Sales To Load 10-15 Passengers - Buy Clear Boat,Clear Boat For Sales,Transparent Boat Product on Alibaba.com https://www.alibaba.com/product-detail/SUNLIFE-Best-Seller-Transparent-clear-boat_1600187905789.html?spm=a2700.7724857.0.0.28261fc5xjffUk.
But note Alibaba's comment "Most transparent boats with cabs are suitable for use, however they are not meant for commercial use." That suggests there
are safety and certification issues, and maybe they are meant for more sheltered inland water.
Unlike most of the off-the-shelf transparent kayaks and canoes, you may need substantial flotation foam to meet reasonably high tourist safety standards - which will interfere with visibility.
(Even a few transparent submarines, at rather high prices.)
Though I assume glass can be more transparent. I wonder how transparent any of them remain after scratches and other wear. And how safe can real glass remain after scratches?
This video youtu.be/12qk67AOqBI points out that it is awkward to go to the bathroom on a transparent boat - a possible concern for tourist boats.
Also - a clear bottom on something off the water (e.g., elevated on pontoons) probably isn't good enough - except at nearly vertical angles, you get "total internal reflection", and can't see underwater - i.e., it would be little better than having passengers on the outside of an opaque boat.