Undulating and amrophous are just two ways to attempt to describe these Amoeba-Shaped Fiberglass Preforms. Once set in the ground, there is nothing revealing of an unnatural pond. The shapeless, or "free-form" designs take the guessing work out of creating an original waterscape shape, and the result is almost nothing short of a true pond! Of all these Amoeba-Shaped Fiberglass Preforms, only the T Model is deep enough for fish Winterizing, complete with an 18-inch depth and a 6-inch shelf at opposite ends. The U and S Models also have 6-inch shelved sections.