American swimmer Haley Anderson won the 5-kilometer open water race Saturday to take the first gold medal of the swimming world championships.
A silver medalist in last year's 10K Olympic race, Anderson edged Poliana Okimoto of Brazil in a sprint finish in the city's harbor.
Anderson finished in 56 minutes, 34.2 seconds while Okimoto took second 0.02 behind.
Another Brazilian, Ana Marcela Cunha, finished third.
The race took place in ideal conditions, with the water 24 degrees Celsius (75 Fahrenheit) and the air temperature between 28 and 29 Celsius (82 and 84 Fahrenheit).
Crowds lined the docks as the competitors swam alongside a line of moored boats and the port.
The men's 5-kilometer race is later Saturday.