Usually is only because of blood vessels breaking in the skin.
Answer:
On the basis of the phenomenon of the degeneracy of codons, the coding of single amino acid can take place by various codons like four different codons, that is, CCC, CCU, CCG and CCA can code for single amino acid proline.
In case, if there is a mutation in DNA, due to which CCA get transformed to CCG, even in such case coding for the same amino acid proline will take place. Hence, one can conclude that at the level of DNA mutation is taking place, however, the same is not getting witnessed in a protein, and that is why such kind of mutations are termed as silent mutation.
No diagram shown, but it would be the fish/any other organisms near or in the shallow part/any part of a pond/lake.
