In general, most "water" simulation products can be poured as deep as desired... but need to be done in multiple layers of 1/8 inch.... you CAN do thicker pours, but they tend to shrink more noticeably than more shallow pours.
Also, consider that after each thin pour, add a few "streaks" of color... greens, blues, browns, etc... then when you have mutliple layers, the water looks really deep and appears to have "flow" caused by the perception of different colors at different depths.
You can also add "bulk depth" by starting off with a layer of clear acrylic plastic... then add a layer or three of clear resin and you will have REAL depth quickly.