Titan Dweevil[]
Two-time Strategy[]
This strategy involves fighting the Titan Dweevil twice, the first time collect all the treasures as you go through the caves and before engaing the Titan Dweevil position either Olimar or the president right next to the geiser, then when it comes to the Titan dweevil only knock off one of its weapons (preferably the Shock Therapist as this is most dangerous), then use the pertification spray to keep it busy while you get your pikmin to take the weapon to the spacecraft, as soon as it has been collected by the spacecraft, switch to the character by the geiser and leave.
Then when you come back the second time you can get to the bottom with minimum pikmin loss as you don't have to worry about the treasures you picked up the first time. Then when you get to the Titan Dweevil there will be more pikmin to face it and one less elemental hazard to worry about.