The first structure you will find in any pond is the dam, then you can start by knowing the history of the pond and how was it built. Many times the dam of the pond is formed by bulldozers pushing and accumulating the soil from the terrain to form the dam, in that case the bottom of the pond is featureless, the only two structural elements are the bottom and the dam. In other cases the terrain on which the pond was built didn 't have enough soil to make the dam out of it, therefore the dam is made from soil that was brought for that purpose, this means that the structural features of the terrain are there, looking around the pond the terrain above water level will tell you where those structural features are, what you see above water level is the same thing that 's underwater. Weeds will also tell you, looking closely you will see that weeds gro in very distinctive patterns, if the pond 's bottom is featureless weeds wil form an expanded weedbed and will grow as deep as they get enough sunlight to grow, if you see an expanded weedbed the bottom is featurelss but in the other hand, wes gro on patches that means that there 's a change either in depth or bottom composition that 's causing the weeds not to grow like a carpet, the spaces between those patches is where the structural feaures are.