Torvus Bog is largely submerged, requiring you to navigate both above and below water. The Hydrodynamo Station and Torvus Lagoon are key areas. Underwater sections will introduce new enemies like the Grenchler and Shriekbat. Your movement is slower underwater, but your weapons still function. Look for underwater tunnels and hidden passages. The Scan Visor is particularly useful here for identifying weak points on aquatic creatures and finding submerged pathways.
You'll need to activate several mechanisms to drain water from certain areas or open new paths. These often involve using the Morph Ball in underwater tunnels or shooting specific targets. Be wary of the Dark Torvus Bog portals, as the underwater sections in the dark dimension are even more perilous, often featuring corrosive water that damages Samus.