This mermaid birthday invitation template turns a seventh birthday into an underwater story: a watercolor mermaid card in teal, coral and seafoam greens, with a casual brush-script name that matches the card's own hand-lettering. The guest page keeps the lagoon world alive from top to bottom — rising bubbles, drifting light rays and swaying seaweed behind frosted panels, a tide-pass mat framing the card with a teal offset shadow, a shell-noted details sheet, a four-cell countdown that hangs like tide tags, and an RSVP sealed with a coral starfish on the page's only deep teal panel. Families planning an under the sea birthday party or a mermaid party theme for a girl's birthday will find the six canonical rows already in place: date, time, venue, RSVP deadline, dress code and parking, with the countdown ticking automatically toward the event date. The template is built phone-first, so the bubbles and waves read just as well on a small screen as on a desktop. Swap the demo details in the editor to personalise it, and the same lagoon palette carries the whole party from invitation to thank-you. The countdown cells are styled like tide tags with punched holes, and every section keeps its own two-line title — a shell-notes kicker above the details, a tide-watch kicker above the timer — so the theme never relies on a single image. Because the page is a single self-contained document, it loads fast on any phone and works with the platform's built-in RSVP form.