We make it harder to propel the boat by adding weight, overfilling our water bottles, or paddling with a bungee rope attached to increase resistance.
Times, Sunday Times (2016)
However, two interproximal grooves did not significantly increase the resistance form.
Aman Arora, Viram Upadhyaya, Sheen J Arora, Ritu Sangwan 2016, 'Evaluation of the effectiveness of auxiliary features on resistance with decreased occluso-cervical height: An In Vitro study', Indian Journal of Dental Sciences