Mr. Sticky's TM can stretch 7-30 times more vs. typical epoxy. A molecular interaction force displaces water away.
Mechanical bonds hold by surrounding object, then hardening.
Some Epoxies cure underwater, most don't bond underwater. No other adhesive bonds if applied underwater without mechanical bond. No No Flexibility and PVC bond required for successful pipe joints. Possibly Liquid glues must harden before water pressure is active. Good Limited Limited Limited Few glues can strongly bond PVC to other materials.