An overall view of the mold:

The PLA positive, after removing the silicone negative, showing the silicone below the surface:

The corresponding silicone negative cavity, flipped top-to-bottom:

The milk chocolate result, although probably not from the same cavity:

The radial gradient on the tummy comes through clearly and, I think, pleasingly, even though it’s only a few layers tall. The threads defining the flipper just above (to the left, in these images) of the foot show where the flipper crosses the tummy and foot level. I didn’t expect the foot webbing grooves to get that ladder-like texture, but I suppose having non-slip foot treads would be an advantage.
If you don’t mind the hand-knitted texture, which I don’t, this process seems perfectly workable.