Towerless Security Button
There are 4 buttons throughout all of the Mermalair that are needed to press the Mermalair Computer's master button. The master button lowers the bridge leading to the Villain Containment System.
One of the buttons is located at the Spinning Towers of Power. From the platform near the Security Tunnel's entrance, SpongeBob can fire a cruise bubble towards the button and activate it, without needing to visit the Spinning Towers of Power at all.