If there’s anything positive to be said about the widespread Xbox Live outages experienced during the busy 2007 holiday season, it’s that Chair Entertainment’s aquatic side-scrolling shoot-’em-up made its way into a good many gamers’ homes. Undoubtedly hoping to capitalize on Microsoft gifting the game to all XBL users for a limited time, Chair Entertainment announced today it would be releasing Undertow’s first expansion pack–Path of the Elect–this Wednesday.

Available for 400 Microsoft points ($5), Path of the Elect packs on an addition five levels to Undertow’s original 15-stage single-player campaign, and introduces a new playable race, the Elect. Whereas Undertow’s campaign primarily focused on the struggle between Atlanteans and marines, the new expansion provides a deeper glimpse at the conquest-driven alien race. The Elect will also be playable in the game’s 16-player competitive multiplayer mode, which itself will be expanded with four new maps.

Undertow: Path of the Elect joins Capcom and A.C.R.O.N.Y.M. Games’ overhead shooter Rocketmen: Axis of Evil on the Xbox Live Arcade this week. Rocketmen will be available on both XBL and the PlayStation Network for $10.