Step 1: Identify the mission.
Swachh Bharat Mission (Clean India Mission) was launched on 2nd October 2014, the 145th birth anniversary of Mahatma Gandhi, by Prime Minister Narendra Modi.
Step 2: Recall the primary objective.
Its core goal is to promote cleanliness and sanitation across the country, including constructing individual household toilets and eliminating open defecation.
Step 3: Rule out distractors.
Tribal welfare, fishermen welfare, and tourism promotion are objectives of entirely different government schemes.
\[ \boxed{\text{cleanliness and sanitation across the country}} \]