Yes - the Lot Adjuster works for that. I have BV, so when I do that, I tick the "Is beach lot" box, at the same time as adding the land.
So... I don't know what it would do if you didn't have BV? At the very least, make sure the terrain is set to match the neighborhood - NOT flat.
Good luck!


Exactly what @simsample said. (And that grid view is freaky! )
You can use the NeighborhoodTerrain cheat right over roads, and raise/lower the whole island. You just can't use it on already placed lots. The area needs to be free of all lots.

I have a tip about how to create smooth beach lots at the beginning of my Build a Pier workshop video. (Cue it up around 4 minutes.) Now... that is for a different hood, but the same idea will work for your island too.

To get your beach lots lower - on your custom hood - I would start with the one place the beach lot did place, and work from there.