Under the Tourist Visa on Arrival Scheme, i.e. TVOA, a group of foreign tourists would be granted with Collective Landing Permits or group visas, when arriving India via air or sea. The permit would have multiple entry facilities and would be valid for a period not more than 60 days.
To avail this facility, the travel agencies (approved by the Ministry of Tourism) or the tourists will have to fill in an online application form.
List of Countries Eligible for TVOA
List of Airports Offering TVOA Facility
For more details about the group visa, check out this PDF:
Tourist Group Tourist Visa on Arrival/Collective Landing Permits for Group Tourists