SIC used to make one... Actually surfed really well and was super stable.
www.standupzone.com/forum/index.php?topic=25948.0
Sunova Skate is one of the closest in shape / idea ... I used to have an 8'2"... Didn't like it as much. I haven't surfed a Shroom so can't speak about that one.
JL do a Superfrank and whilst it doesn't have the typical Fishy tail, it rips.
I'd even spoken to Scotty @ Smik to maybe make me one a couple of years ago... he was testing one out a while back: www.instagram.com/p/BvD3pRgnHSL/
Assuming you were serious - which does not seem likely :-) - that just "searching 101". You need to disambiguate requests.
For instance if you search for the animal "Jaguar", but find only reference to the car maker in first hist, just exclude the cars, type: "jaguar -car -automobile -suv"
In your case, just type "fish paddleboard -fishing"
I designed a Twinzer Mid length with Kami a while back, but have not got it made yet... Twin fin with tiny canards on the outside front. Centre fin plugs for a MR style centre fin for when it gets big....
www.evo.com/outlet/fins/futures-twinzer-twin-fin-set
Nice.
But I mean proper flat rockered fat arsed twin keel finned freakazoid fish...
Why not as a sup???
Looking at fishy surfboards like Lost RNF or Hydra, the outlines don't look too dissimilar (to my eyes) to wider tail performance SUPs on the market, like an Infinity Bline/RNB, JL Worldwide, etc.
is there a big difference I'm not noticing?
To my eyes yes
But yeah as colas said supply and demand plus people don't have twenty inch long feet.
And I forgot to add that for most people, small waves implies a longboard shape. Very few people are going to try a fish shape (relying on tail width and clean water exits for power in waves rather than length), reducing the market.
Also, I had an AHD Sea Lion. It was hard to surf well because of the huge tail, the low tail rocker designed for windsurfing planing, and the deep swallow that prevented to place the rear foot aft enough. An excellent compromise Windsurfing/SUPing, but as all compromises it had limitations.
Yeah OK.sounds like it just doesn't work so well in surf in the original pure under developed form. But can be palatable with a few subtle added standup herbs and spices, like Sunovas Skate.
But now I think I have seen a Sealion in action before, was a day of mushburgers. The dude was connecting up sections pretty well, better than others on longer all rounders. Did look fun.
My smaller quad fin board feels just like a "modern" surfboard fish I have surfed even if proportions don't look like a classic keel twin. Tail is pretty wide at 18, a down the line machine. As colas said challenging back foot placement if you want to tighten your turns past 90. Still works in bigger surf if you engage the forward rail with the front foot kind of like... a fish surfboard.
I've been riding this 7'6 for the last year, would definitely class it as a fish but not a twin keel deep cut swallow fish tail as such. I did rise the first Nah Skwell proper twin fin split tail fish pre AHD version and it surfed really well. As long as you kept your back foot mobile it turned well, not as tight but could get some flow out of it!
As far as performance fish/twins go found these a while back never hear much more other than the Pro Mo Rawson models a few years back. They all look fun! Love to try an assy, next custom maybe...