I generally enjoy fishing in this game. I've been a Master Angler for a while now, and I often go and fish the DLC zones whenever new content is released. So, I already went and completed the fishing achievement for Northern Elsweyr, after the chapter's release last week.
https://steamuserimages-a.akamaihd.net/ugc/803243228396070938/6998D1614186BEB207E8331560ADAF4E7D4A59C6/
The fishing in this zone was... interesting. I wanted to flesh out what I found after spending several hours fishing in the zone. Right off the bat, I knew that there would be some unpleasantness involved, because all of the holes were river holes. Zones that only have one type of fishing hole are more grueling than those that have a variety of water types. That's because there are now several blue fish for the same water type, meaning not only do you have to deal with the low odds of getting a blue fish on any give cast, but you have even lower odds of getting a specific blue fish if there are multiple for the same water type. So if there's just one blue river fish in a zone, when the odds come up in your favor and you pull a blue from a river hole, it will be the one you need. If all the holes in the zone are river holes, any time that you are lucky enough to pull a blue, you have a large chance of not getting a specific blue river fish for that zone. So your odds of getting all the fish you need for the achievement are significantly lower in a zone with only one water type, than in a zone with three or four different water types.
Usually, ZOS only makes a zone all one water type when it's the only thing that makes sense. For example, Coldharbour and Clockwork City are both all foul-water zones, because they each only have one type of liquid found in the wild in those zones, and in both cases (blue glowy stuff and oil), that one type of liquid makes sense to be foul water. So, I assumed when I started fishing in Northern Elsweyr, that the situation would be the same, that the only water features found in the zone would only make sense as river holes. And I noticed that ZOS definitely took steps to make a one-water type zone more palatable here. The places where fishing holes are found in the zone are some of the most picturesque and pleasant I've encountered while fishing in any zone. Like this, for example:
https://steamuserimages-a.akamaihd.net/ugc/803243228396070139/DCB2D63D60B1EBF47E0FD55BE98008550DA2FF00/
It's a lot less boring to be fishing for hours in a landscape that looks like that than in the monotony of Coldharbour (there's a reason why people going for Master Angler hate that zone). I also noticed that there were an absolute ton of harvesting nodes located near fishing holes in Northern Elsweyr, much more than I've encountered when fishing any other zone. So the stunning scenery and plentiful crafting nodes I encountered as I fished the zone helped some in combating the monotony of it being a one water type zone.
The other thing I encountered, however, was the realization that there was no reason whatsoever for Northern Elweyr to be all river holes. There was no reason for ZOS doing that, unlike in Coldharbour or Clockwork City. ZOS is often a bit arbitrary with how they classify certain fishing holes (like with the random foul hole in the lake next to Riften that's just feet from a lake hole), but they generally follow a basic guideline. Fast, running water is river. Large, contained, still bodies of water are lakes. Oceans are ocean (simple enough). And foul can be either small, shallow bodies of water surrounded by dead trees and animal carcasses, or places where ocean and freshwater sources meet. Here's a map of the fishing hole locations I found in Northern Elsweyr. There may be a couple holes I don't have on here, but this is the overwhelming majority of the fishing hole locations in the zone.
https://steamuserimages-a.akamaihd.net/ugc/803243228396071314/A0D2B62D21993F39FFC60791920B5BBB3FBF49B5/
Looking at that, most of the holes you see in the northwest and southwest are in water that very clearly had to be river. A couple in the east are as well. However, the very northwest 3-4 holes, a group of another 3-4 holes in the southwest, and all of those holes in the south-central portion of the map near Merryvale Farms are in water that very clearly should have been lakes. There's no way to look at those sources in person and think they could be anything other than lake holes. So that's a good 20 fishing holes right there that obviously should have been lake holes, but were made river holes for no reason. In the east, most of those holes you see should be foul holes, as they're in small, shallow bodies of water surrounded by dead trees or dead animals. In addition, that one isolated hole in the northwest below all the other clusters of fishing holes is in a water source that could only be foul water. So that gives us a good 30 or so river holes, 20 or so lake holes, and 6-7 foul holes that are already fishing hole locations. Without adding holes to any of the water sources on the map that don't have any (most of which would make sense as foul holes when you see them), ZOS already had plenty of spots to make a balanced zone with three different types of fishing holes.
After fishing it all, I realized that there was no reason for Northern Elsweyr to be a one-water type zone. In fact, they had to break their usual norms to make it one. A large chunk of the fishing holes in the zone don't make sense as river holes, but that's what ZOS made them. So all the aggravation of having to deal with the lower odds inherent in a one-water type zone was totally unnecessary. It's unclear why ZOS made the fishing in the zone this way, it didn't make sense to, and added some completely pointless unpleasantness to fishing in the zone.
With the gorgeous scenery and nearby crafting nodes, Northern Elsweyr could have been one of the single best fishing zones in the game. But by breaking their own guidelines and making it a one-water type zone when it shouldn't have been, ZOS shot themselves in the foot. It's a completely self-inflicted wound, and I bring it up so that ZOS realizes that there's no reason to make this type of mistake again in the future. I still enjoyed my fishing experience there overall, but it simply wasn't as good as it should have been, and it's baffling that ZOS made this error with the zone when all the pieces were there for them to absolutely nail the fishing in Northern Elsweyr.