The Kraken is guarding the bridge, so you can't cross the ravine in Forgotten Bay. You'll need to complete all quests on these islands to get pearls needed for the bridge, 2 for each island:
  • Selvil;
  • Aguado;
  • Kelonia;
  • Octopod.
Load them to your ship, bring them home, and unload them MANUALLY. The pearls are in the Cargo tab >> Artifacts.
Continue exploring the islands to collect all pearls and unlock the bridge.