Ambergris is an old substance that at one point in time was used to make beauty products such as ladies perfume. It comes from the intestines of a whale and it can be used to attract mermaids. It is also an ingredient for a potion, which causes the effect of the Moon of Fifty Years.
In Mako Mermaids it was last mentioned by Mimmi. Rita keeps a bottle of it with her potions. Mimmi notes that it is very powerful.
- While in the episode the ambergris was yellow liquid, in real life ambergris is a solid, waxy, flammable substance of a dull grey or blackish color.