User blog comment:Plexioth- xD/Monster Hunter 3 Ultimate/@comment-1758220-20120429160759/@comment-71.162.209.135-20120429180342

Lagiacrus sub goes into the water when its weak to get to area 12 of D. Island. You can try to fight it underwater but it just ends up limping away before you can or it attacks you and then limps away. So lagiacrus sub isn't fully land based.