Reference article
Crossing the Lava
Use her Bucket of Water on the lava stream.
Quest guide
Step 1
Talk to 
Misty in Volcano Town and challenge her to a race.
Step 2
Win the race to collect the 
Bucket of Water.
Step 3
Return to the lava stream beside Misty and pour the water onto it.
Step 4
Cross the solidified stream to continue exploring Volcano Town.
Starting it
Talk to Misty and race her.
Reward
Bucket of Water and a solid crossing.
Things to know
The water creates a crossing through this story barrier; simply learning Swimming does not clear the lava stream.
