concrete bonding adhesive
Ah yes, what the Europeans call(ed?) the Flevopol method. It winds up looking similar to results from the Titebond method.
No, I wouldn't immerse that, but I did a few acrylic copolymer (concrete fortifier) backgrounds back in the 2000's and they stood up well to misting & high humidity. A bonus - if you have a piece spall off repair is easy