DYN is most often a pool discipline in which the freediver travels in a horizontal position underwater attempting to cover the greatest possible distance. Any propulsion aids, other than fins or a monofin and swimming movements with the arms, are prohibited. Dynamic with fins is the most common of the horizontal distance disciplines because of the specific means of propulsion ;long fins or monofin. For a performance to be officially recognized there are minimum depth and length requirements for pools. Pool competitions most often comprise a performance in DYN, DNF, and STA but some competitions are a combine’ of DYN and STA.