Most people are familiar with the epoxy in the two tubes and get mixed as you depress the plunger. The epoxy has two parts and the bonding is done through a chemical reaction when the resin and hardener are mixed.
There are epoxies designed for stone and brick. And they work underwater. The resin and hardener for these are thicker so they don't run. Each component is a different color to assist with the mixing. As you mix them, the color changes to a third color, indicating that they are properly mixed.
These paste epoxies have a long shelf life and hold great. One word of caution - when putting the lids back on the cans, be sure to get the proper lid on each can. If not, you'll never get the lids off.