If you want to turn values below 0 into NoData and leave the rest untouched try this expression in Raster Calculator:SetNull("depth_layer" < 0, "depth_layer")
If you want to change values below 0 into some value (eg. 0) try this:Con("depth_layer" < 0, 0,"depth_layer")
If you want to just see which values are below 0 use simply:"depth_layer" < 0