The film continues the adventures of Percy Jackson (Logan Lerman) and his friends as they journey to the eponymous Sea of Monsters to retrieve the Golden Fleece in order to save the tree barrier that protects their home.

Lerman, Brandon T. Jackson, Alexandra Daddario, and Jake Abel reprise their roles from the previous film, while Nathan Fillion and Anthony Head replace Dylan Neal and Pierce Brosnan, respectively.

Seven years before the events of the film, young Annabeth Chase, Thalia Grace, Luke Castellan and Grover Underwood were pursued by monsters on their way to Camp Half Blood.

When Thalia sacrificed herself to save her friends, her father, Zeus, honored her act by turning her into a tree, which formed a protective barrier around the camp, keeping everyone inside within a safe zone.

He is joined at camp by a young cyclops named Tyson, a previously unknown son of a sea-nymph and Poseidon, and therefore Percy's half-brother.

As it will involve crossing the Sea of Monsters (Known to humans as the Bermuda Triangle), camp counsellor Mr. D denies them, but then claims the idea as his own and selects Clarisse for the quest.

Meanwhile, Percy consults the Oracle of Delphi, who tells of a prophecy that a half-blood of one of the three elder gods will one day either save or destroy Olympus.

As Luke begins reviving Kronos, Percy escapes capture and confronts him, aided by Tyson, who survived his wound after being healed by the water, as he is Poseidon's son.

The group returns to camp, where Chiron expresses uncertainty as to whether Percy has fulfilled the prophecy by preventing Luke's plan to destroy Olympus.

The website's consensus reads, "It's pretty and packed with action; unfortunately, Percy Jackson: Sea of Monsters is also waterlogged with characters and plots that can't help but feel derivative.

[33] Jim Vejvoda of IGN rated the movie a six out of ten: "There are worse sequels than the CG-heavy Percy Jackson: Sea of Monsters, but it's just such overly familiar territory.

[35] James Rocchi of ScreenCrush wrote that the film "is hardly the stuff of legend, but by keeping the plot straightforward and the storytelling clean, it's an odyssey the intended young audience will be glad to take.

"[36] Marsha McCreadie on RogerEbert.com rated the film two and a half stars out of four, calling it "a gentler-spirited, less flashy enterprise, though it still presents a natural world that can morph at the whim of a god.

"[37] Andy Webster of The New York Times commented: "Sea of Monsters is diverting enough — the director, Thor Freudenthal ... is savvy with effects and keeps his young cast on point — but it doesn’t begin to approach the biting adolescent tension of the Harry Potter movies.

"[41] Josh Bell of Las Vegas Weekly lambasted the series as a whole as "a thoroughly second-rate franchise ... with movies like Sea of Monsters, it can probably continue in acceptable mediocrity for years to come".

[46] "My Songs Know What You Did in the Dark (Light Em Up)" by Fall Out Boy and "Cameo Lover" by Kimbra were featured in the movie but are not included in the soundtrack.

[51] The rights to the Percy Jackson novels were transferred to Disney following its acquisition of 21st Century Fox in 2019, upon which Riordan pitched a new adaptation in September of that year.