@IreneSwift
Hello! I was intruiged and did a test run. This is what I did:
In an unmodded game and in a fairly new save (week 4) my sim was already in the normal future, and did not know how to fish. When examined, the fishing spots/water will say "unknown fish", until the skill level for that particular fish is reached, and then show a name, 'goldfish' etc.
The two fishing spots I used throughout was in the canal right next to the 'EP-XI Import Gallery' and the pond/lake next to the Zephyr station, Reality Road in the Waste Land, fishing spot at the other side of the water than the station. All 4 times I used them both. I fished during daytime as well as nighttime, the temperature of 4 degree Celsius/40 degree Fahrenheit is only during nighttime, in the fall, at around 00:00 - 01:00 'military time'/12-01 a.m.
I first levelled up my sim's fishing skill to 10 (with Multipad 6000 while partying) then went back to 'current time', changed the future to dystopian, went there and tried to fish.
The garbage was in the water, and when 'examined' showed that '3-eyed fish' were there, and fishing it was successful.
My sim then went home to current time, changed the future to utopian, went to the two fishing spots and they both had flowers on the water, 'rainbow snail' when examined, and she caught several of them.
This was summer.
Then came fall:
She went back to to current time, changed future to 'normal', went to the future, bought a house ("Campus", the big one outside of the city, near the waste land), went back to change to dystopian future and back again, chose the bought house as 'home lot".
The garbage was in the water, examination showed '3-eyed fish', and fishing was successful.
She went back, changed to utopian, chose the bought house as 'home lot' and since it was night went to sleep. Meanwhile I looked for the flowers in the water, but could not see them until after a while (a couple of sim hours, fast forwarding because the sim was asleep). When morning came she went there, examination said 'rainbow snail' and fishing was successful.
I do not know why I did not see the flowers at first, it could be that they weren't there or that my eye could not catch them (highly possible). The flowers are smaller in area than the garbage and during nighttime are blueish, as are the waters, and my graphic settings are on low/middle for the most part. From afar they look more like an ordinary fishing spot with jumping fish as the most visible sign.
I searched for the problem (unsuccessfully), but found one comment (on Carl's Sims 3 page), saying that rainbow snail had been found in a rainbow knoll, so my sim dug a lot of them out. (They are small beige dirt mounds in the green area outside of the city, visible in map view and when close up have a little rainbow attached). In a week she found: rainbow stones (17), rainbow trout (12), rainbow butterfly (12), pot of gold (11) and rainbow bug (6), but no rainbow snail. It does not mean they can't be found that way, it took half a week until rainbow bug appeared.
Another comment (somewhere) said a witch could transform an object to a 3-eyed fish (I have not tried this).
If in a bed in the future 'dream' is chosen, the option 'sleeping with the fishes' will give several random fishes in the sims inventory, upon wakening, that are not bound by the sim's fishing skill level, or world exclusive. My sim dreamt for a week, but got no 3-eyed fish nor rainbow snail. Skilling in advanced technic gives more dream options, I think the fish alternative need around level 5, sorry, I did not pay attention to it.
Hope someone else has a solution/explanation :smile: