Yes, these are the foundations that come with the island paradise patch! I told myself a while ago I'd wait for Twallan to update his mods before I downloaded it but these features were far too tempting! Besides, I'm busy with my internship on weekdays (at least until August) so I won't be simming long enough to be bothered by the wait.
I haven't had the chance to look at changing the heights of foundations yet, but I did try out the new stilted foundations and placing lots on water. Technically, they can only 'partially' be placed on water but so long as you've snagged a teeny piece of corner you can push the lots pretty far out.
I'm still getting a feel for Dragon Valley so I decided to try building there first. I'll be able to do some fun things with Island Paradise later on though. This was the spot I chose, just on the riverbank...
The method for placing these is surprisingly intuitive, they're placed just like normal foundations! The only thing you may still want to do is smooth out the land around it with the terrain tools, as there will probably be some distortion like what's seen here where the platform kisses the bank.
And this was how I set up the outside walls (this build has since been finalized and my sims are living in it, but it's not very fancy since they've only been living in it for a couple of sim days so they're no reason to take pictures yet).
You'll need to make sure you add stairs or sims won't be able to get up on the foundation (and subsequently complain about it). Gangplanks are coming with the expansion on Tuesday, so until then this is the only way (short of teleporting of course). A few flowers and shrubs should help hide the gap if you really don't like the look of it.