Microsoft plans to release fresh downloadable content for Lost Odyssey in Japan on 10th April.
It'll involve travelling to a secret underwater research facility in your Nautilus ship, according to Watch Impress, and will cost 400 Points (GBP 3.40 / EUR 4.80).
Judging by a rough translation, the content opens up on disc four and sees you puzzling your way through the facility while fighting things like fish monsters.
The lure for doing all this is an accessory that teaches you a powerful ability. You will need to amass 999 skill points while wearing it to learn the skill, which appears to be something to do with lowering MP consumption to zero.
Microsoft has been contacted for comment.