According to Official Guinness Records,
The most watermelons chopped on the stomach in one minute is 55, achieved by K.V Saidalavi and K.P Gireesh (both India), in Kumbidi, Kerala, India, on 10 April 2018. K.V Saidalavi, and K.P Gireesh were also part of the previous record for the most number of layers on a bed of nails.
For a complete list of 2018 records, please visit 2018 Guinness Records in India.