The aim of the present study was to compare swimming performances of successful finishers of the 'Triple Crown of Open Water Swimming' from 1875 to 2017, assessing the effects of sex, the place of event and the nationality of swimmers. Data from 535 finishers in 'Catalina Channel Swim', 1,606 finishers in 'English Channel Swim' and 774 finishers in 'Manhattan Island Marathon Swim' were analysed. We performed different analyses and regression model fittings for all swimmers and annual top-5 finishers. Effects (sex, event, time, nationality) and interaction terms (event-time) were examined through a multi-variable spline mixed regression model. Considering all swimmers, we found that (i) women were approximately 0.06 km/h faster than men (p = 0.011) and (ii) Australians were 0.13 km/h faster than Americans (p = 0.004) and Americans were 0.19 km/h faster than British (p<0.001) and 0.21 km/h faster than Canadians (p = 0.015). When considering annual top-5 finishers, we found that (i) women were 0.07 km/h slower than men (p = 0.042) and (ii) Australians were not faster than Americans (p = 0.149) but Americans were 0.21 km/h faster than British (p<0.001). Our findings improved the knowledge about swim performances over time, in the three events, considering the effects of sex and the nationality of swimmers.