Retrospectively, Mermaid vs Sailor received generally positive reviews from music critics, who felt it was indicative of Diamandis' potential as an artist.

Despite attending several auditions, she was unable to secure roles and began self-composing and producing demos using the digital audio workstation GarageBand on her personal laptop computer instead.

[5] Unofficial record label Story Tailors productions later created a bootleg version of the release on 10" vinyl in November 2009, limited to just 35 copies.

Re-recorded versions of "Seventeen" and "Hermit the Frog" both appear on her debut studio album, The Family Jewels (2010), although the former song is only included as a bonus track on the Japan deluxe and United States standard editions.

[12][13] Mermaid vs Sailor opens with "Seventeen", a song that tells the story of an undisclosed event that occurred in Diamandis' life when she was 17 years old.

"[4][17] In a 2015 interview with Rolling Stone, Diamandis revealed that "Plastic Rainbow" was the first song she had ever written at around the age of 19 or 20, which gave her a feeling of wanting to become a songwriter.

Rick Fulton from the Daily Record suggested that the EP generated extensive exposure for Diamandis as an artist and felt it helped to establish her as "yet another MySpace success story".

[19] The popularity of her Myspace profile and Mermaid vs Sailor led to her discovery by Neon Gold Records head Derek Davies, who worked with Diamandis for a period of six months.