As per my knowledge Aqua is a template just like we had Sunburst in CIM. Different look and feel.
From Cisco Document:
About Aqua Template Sets Template sets consist of CSS (cascading style sheets) and JS (JavaScript) files. The CSS files control the look and feel of the Chat Console. The JS files contain the business logic used to render data in the Chat Console. Templates are also used to determine what information is requested to identify the customer (such as name, email address, phone number). You can also compose messages that the customer will see under certain circumstances (for example: if they request a chat session out of hours). An entry point can be mapped to multiple template sets and multiple entry points can use the same template set. The template sets for, Aqua and Aqua (docked), are shipped with the application and can readily be mapped to any number of entry points. The template sets are managed from the web server and not from the Administration Console. What Makes up an Aqua Template? A template consists of a set of pages that are designed to work together. Typically, a chat template has the following pages: A pre chat form The chat area Post chat survey form The off-hours page The alternative help options page. All these pages can be customized to meet your business needs.
Please find the link for reference.
https://www.cisco.com/c/dam/en/us/td/docs/voice_ip_comm/cust_contact/contact_center/enterprise_chat_email/enterprise_chat_email_11_6_1/Maintenance/Guide/ece116_userguide_administration_chat.pdf
