Pirate Queen's Quest
In the Risky route, the Techno Baron was able to recapture and brainwash Giga Mermaid once more, but Risky frees her again. Risky insists that she's still evil, that she didn't free her on purpose, and that the Giga Mermaid now owes her a favor. Despite these claims, the Giga Mermaid still smiles at her once she's freed, and makes no objection to Risky claiming her next Dynamo component.
Friends to the End
As part of Bolo, Sky, and Rottytops' quest, they end up having to fight Shantae's memory of the Giga Mermaid. Rottytops and Sky ask Bolo to give them a strategy for fighting her, but all he can remember are her looks, frustrating his companions.
Boss Fight & Strategy
Initially, the Giga Mermaid is chained to a pair of massive pillars, struggling in vain to free herself. Using the platforms and chains around the pillars, Shantae must destroy the six locks connected to the chains holding the Giga Mermaid.
To complicate matters, the Giga Mermaid periodically releases electricity-based attacks from the gem on her forehead. Initially, she fires a massive orb that slowly moves towards Shantae; the half-genie heroine will usually have to abandon her attack on the locks to avoid being hit. As the battle drags on, the giant mermaid may fire several smaller orbs that move towards Shantae in short bursts; once again, she should abandon her attack on the locks in favor of leading the projectiles around the arena until they vanish. She can also summon lightning bolts that travel around the arena; Shantae can use the platforms to keep ahead of them.
When the last lock is destroyed, the Giga Mermaid will break free of her chains, destroying the pillars in the process. After a short lull, the second phase of the battle begins.
The Giga Mermaid, still under Techno Baron's controls continues to attack Shantae. She mainly attacks by appearing on either end of the dock and summoning lightning; either a single bolt from her gem or a barrage of bolts that strike the ground. The former is telegraphed by a glow in her gem, while the latter is signaled by markings appearing on the ground; either way, Shantae should make sure she's out of the line of fire. She can also dive underwater and attempt to slam her tail on Shantae; she'll pause just before striking, so use that time to get clear.
In between dodging attacks, Shantae must attack the Giga Mermaid's gem to deplete her health. This is primarily accomplished by using the structures that briefly emerge from the water when the Giga Mermaid appears on the dock; Shantae can climb up the structures and jump at the boss to attack her gem. Spitfire is an effective alternative for dealing more damage in a shorter amount of time, but magic limits could make it difficult to finish the Giga Mermaid in this way.
Giga Mermaid's attacks have been modified to increase the difficulty. In her first phase, she attacks more frequently, and her projectiles move faster. Her lightning attack will now instead strike the top-left / top-right of the stage and will travel in the opposite direction around the stage (counter-clockwise if top-left, clockwise if top-right).
In her second phase her lightning strikes will attack more quickly and the hook/platform stage will be risen from the ground for a shorter amount of time.
Giga Mermaid is a gigantic mermaid, with light green skin, long dark blue hair that runs past her hips, fish fin-like ears, and blue eyes. The top of her head is adorned with two massive jellyfish worn as hair accessories, along with a large blue jewel on her forehead. She wears a light blue strapless sea shell bra. On her waist and arms are gills. She has a 'belt' of light blue fins around her hips, and large pink fins poking out from underneath it. Her tail is dark green in color.
Giga Mermaid is initially hostile, due to being captured by the Techno Baron, and attacks anyone who approaches. Once she is freed, however, she appears to be rather friendly and generous, even allowing Risky Boots to collect her next Dynamo component with no objections once the self-proclaimed Queen of the Seven Seas saves her from reimprisonment at Techno Baron's hands.
The Giga Mermaid's eyes and forehead gem appear to change color with her mood - blue is her true kind personality, red when she was enraged and under Techno Baron's control.
- One piece of the Giga Mermaid's concept artwork gives her a more sinister appearance, with Shantae fighting her on a series of floating rock platforms. While Half-Genie Hero handled the boss fight differently, the second phase of the Empress Siren's fight in Shantae and the Seven Sirens ended up using the concept.
- Some of the concepts for Giga Mermaid showed she had pigtails. This could have served as inspiration for the redesigns of the mermaids in Half-Genie Hero, who had loose hair in previous games.