I followed @topp 's guide for moving sculpted beach lots - thank you for that!!!
Everything worked beautifully. Or so I thought.

The issue I'm having is the water isn't "flooding" the lot properly in hood view? It looks fine from in the lot.
Yes, I have made a structural change (added a wall) and exited to the hood and back. Shoot! I even reloaded the hood a few times...
Hood view just won't show the right coastline.

Anyone know a way to fix it?

I'm glad you found the tutorial useful! Unfortunately, the game has always made hideous-looking lot impostors. They simply can't draw non-straight shore line well enough. Here's a few examples to show you that you're not the only one having that issue:

Here are Swaying Palms and Village Residence on-lot:





And here's how their lot impostors look like (lot 17 and lot 20, respectively):





The worst part is that the more non-straight the shore line is, the more flicker there is in neighborhood view as you move the camera, i.e. Swaying Palms flickers way more than Village Residence.

One thing that I can think of (but I haven't tried this myself) is adjusting some graphics settings through LD's RPC Launcher:

*sigh* OK. Thank you.
I might try straightening it a bit more then.
I was just so excited that the original sculpting stayed, that I didn't want to redo it. But, I think it needs a bit of fixing.
I don't use any of LD's "new fangled" thingies. I like the old-school vibe. I just want to push it for all it's worth.

Thank you!

@topp Here's another one though... it's a much simpler build. Yet, it still has a problem. How can I fix this? The water will NOT fill that rectangle!
The portals are all in a snug line, straight across, on flat ground, where the "seafoam" line is. There is nothing hidden in that open space. The water fills in on the edges but not in the middle.
I started with a regular beach lot. Then I un-beachified it with the Lot-Adjuster, moved portals, built the pier, sculpted/moved the water line, re-beachified it.... Gah!
Help?

Could it have to do with the fact that I started on a larger lot and shrunk it so I could get the gently sloped sides?

Have you tried not unbeachifying it? Maybe something got messed up then.

You can't build the pier over the water without unbeachifying it...
(Thanks for thinking with me though!)

You say you've shrunk the lot - I think that's where the culprit is, but I'm not sure I can word my thoughts clearly right now (there's a RL project taking away my last bits of sanity), so bear with me.

There are several ways that we can attack this problem. The culprit is either in the way lot was shrunk, or in the neighborhood terrain geometry underneath the lot.

1) The way lot was shrunk

From my tutorial on building piers on beach lots, here's a picture:



Notice how the sea part is 12 tiles long (viewing from street to the sea)? And the beach part is 8 tiles long, and the normal "lot" zone of the lot is the biggest out of the three. Now, here's the brainfuzziness kicking in - I'm not sure if that's a standard for all beach lots ever, or just that one lot I was building on, of those specific (unknown) dimensions.

However, your lot seems to have those dimensions mixed up - the normal lot zone is the smallest and only up to a few tiles from the street. The sea part, however, is huge.

I think you shrunk the lot from the wrong side, maybe? I'm not 100 % on this - can you try marking the areas of your lot like I did in the picture? The beach area should be the area where you'd get beach interactions - build a sandcastle, sunbathe etc. Then there should be roughly 4 tiles that are unclickable (on classic beach lots, that's the slope as the sea gets deeper) and then the rest of the lot should be with just a "swim here" location interaction. If the sea area of your lot is truly something big, then I suggest expanding the lot back to what it was, and shrinking it from the other side perhaps? Or (the potentially easier solution) just sculpt the terrain to account for the waterless area (e.g. a small hill)...

2) The neigborhood terrain is not flooded enough underneath the lot

Instead of trying to redo the lot shrinking, you can perhaps mess around with a much simpler approach first - what's under the lot, when you move the lot away (either by move lot tool, or by temporarily moving it to the lot bin). My Swaying Palms lot is properly underwater where I wanted it to be underwater due to the underlying neighborhood geometry (the terrain was submerged there already, before I had even moved the lot over there using LotAdjuster) so it's not true that the lot area is never floodable. However, the specific terrain shape and distance between the street and the sea, as seen in for example Twikkii Island (the neighborhood I made the tutorial in) makes it so that the water doesn't really get that high/far - so practically, the lot area remains dry.

You can try moving the lot out of the way and messing with the neighborhood terrain using modifyNeighborhoodTerrain cheat from Free Time.

This is what I may end up doing. It's not what I want - but it may be the best I can do for now.

Thank you for thinking with me @topp .

I shrunk the sides of the lot - primarily to get rid of the "drop-off" on the sides of freshly placed beach lots.
...and I'm going for "realism" in this hood - so beaches along Florida's Gulf Coast (which is affectionately known as the Big Bathtub.)
I wanted a long shallow sea area and a short beach/land area (with a looooong pier.)

If I move the lot, the smooth sides (the sculpted gentle incline I built) will be destroyed.

Maybe the problem is the game doesn't want my beach lot the way I want it to be.

I will try building a similar beach lot idea in a place where the ocean is deeper - but I don't think that is it.
I think maybe beach lots need to have a wider swath of beach/land than what I want to give them.

Ding ding ding! Most of my Felicity Island lots that have non-standard beaches are just good for the looks - the game goes insane trying to understand that I just want my Sim to soak their feet in the shallow ocean there, not to swim laps dammit! But alas, the way EA thought of beaches was probably like, Beach The Lot Like This Or Die.

Edit - I kept thinking about this one mod or something that made the beaches look smooth and still functionable. What was it called? Why would I take it out!? - and then I remembered - it's a whole separate game, The Sims Castaway Stories. It has all the mechanisms required to make the beaches look natural. If there's water, Sims know it's water and swim or soak their feet, depending on the depth of the water. I wish I could port that mechanism to TS2...

And bring the swimmable pond with it!