I like the depth, one thing to consider is if you go too shallow you lose the ability to float over it. I have a baja shelf that is almost 1/3 of my pool, I did not want to lose that much floating surface area. There are plastic chairs we looked at with the seat at about 12-14" so they are perfect for us to sit in. We aimed at 16-17" but ended up about 18" when all was said an done. They aren't going to nail it perfectly, well at least my builder does not understand basic measurements. a couple inches either way won't make a difference. I would shoot for 12" or 18" I think 12 is way too shallow for me, but at about 6'3" when I am sitting on the baja shelf the water is just under my chest. We tried different depths several times at our timeshare in Maui, I always came back to the 16-18" depth.
the chairs we got are the Adams Mfg Corp Resin Stackable Patio Adirondack Chair the seat is 14" high in the front and about 11-12" in the back. I don't plan to place a recliner in the water as you would need to go about 9-12" in water depth, that was too shallow for me.
YMMV.