It is quite clear that the Coral Siren and Shantae are enemies. Unlike her fellow sirens, however, the Coral Siren is much more serious, much like the Empress Siren herself. Although smaller than the other sirens, she is very intelligent, building her own mechanical suit and doing repair work on the Sunken City, though she does have a bad temper when she's called a seahorse.
The Coral Siren is the boss of the Coral Mines. In battle, she attacks by launching bombs, charging into the foreground, and performing big leaps from the background plane to the gameplay plane. The giant leap takes around three to five seconds to complete. When she does the latter, Shantae must dig holes in the floor via her Gastrol Drill transformation, and has three or five seconds to do so before she gets crushed. Drilling the holes causes the Coral Siren to get stuck when she lands. When Drills gets stuck, Shantae can strike at the Coral Siren's weak points. As she loses health, she is less likely to perform the giant leap. Shantae can also use the Gastro Drill transformation to dodge the charge attack that the Coral Siren can do.
Her Monster Card regenerates 1% MP per second when equipped.
While her mech is large enough to be on-par with her tougher cohorts, the Coral Siren herself is rather small.
The Coral Siren's appearance inside her mech was up for debate for quite some time, before it was revealed on Twitter in full.