In Venus and the Tail of Courage, Venus, now studying to become a Sea Witch, faces her biggest challenge yet: passing a crucial exam to graduate to Merddle School where she will train as a Spy Witch.

With the pressure mounting, Venus and her friends must navigate a perilous group rescue mission in the Queendom of Mermantis using secret mermaid magic for the first time. Mermaids use "inner technology" based on the sharkras and magic body, whereas earthwalkers use outertech, such as screens and gadgets.

As the last squad to take the test, Venus fears she'll let her friends down. But with the help of her friends Rootsy and Dawa, and guidance from their teachers, Venus discovers the power of courage, inner vision, and joy, unlocking her 'innertech' to shapeshift her tail into legs, unravel a curse, and restore balance between mermaids and earthwalkers.