I am working on organizing and cleaning some lake bathymetry measurements. In my data sets, the lake boundaries were digitized, and the vertices of the boundaries were used as points where the depth value was zero. Those points were combined with the actual depth measurements, and a bathymetry surface was generated using Spatial Analyst>Interpolation>Natural neighbor. In general this worked well, however, in some areas where the slope of the lake bottom was steep, or the lake boundary was complex, the generated surface spills over the lake boundary, and the contour lines generated from the bathymetry surface go over the lake boundary, or obliterate an island.
I am looking for a better method.