The Seahorses, which had previously been in existence as a youth soccer club since 1983, joined the PDL in 2001, and were successful immediately, finishing second to Orange County Blue Star in their debut season with a 13–6–1 record.

The developing rivalry between the Seahorses and Orange County Blue Star continued in 2005, when yet again the men from La Mirada finished a close second to their all-conquering Southland neighbors in the Southwest Division standings.

The Seahorses began the season with a five-game winning streak that included a 3–0 trouncing of California Gold; however, they did not manage to defeat – or even score a goal on – their rivals in their three games, losing 4–0, 3–0 and 3–0 to the eventual divisional champs.

Nevertheless, the Seahorses were clearly the next best thing in the southwest,[citation needed] and enjoyed several impressive wins (including a trio of 3-0s over San Diego Gauchos, Nevada Wonders and Fresno Fuego) in the second half of the season.

They enjoyed their revenge over Orange County Blue Star with a 1–0 win in June, making up for a 4–1 thrashing earlier in the season, and put an end to the San Jose Frogs' playoff chances with an impressive 3–1 home victory in mid-July, but finished the year with a 5–2 hammering at the hands of Fresno Fuego, and a disappointing bottom-of-the-table clash with Lancaster Rattlers on the final day of the season which ended in a 1–1 tie and managed to keep them out of the basement spot.

The Seahorses ended their season in 9th place; Chris Leiva, Diego Mejía and Cristian Rus were the joint top scorers with three goals each, while Scott Lucky led the assist stats with 2 to his name.

The Seahorses drew eight of their sixteen regular-season games, and were made to rue their matches with Fresno Fuego and Ventura County Fusion in which they conceded a 90th-minute equalizing goals when they looked odds-on to win.