The River Seine water quality has dropped again, forcing another disruption to triathlon at the Olympics.

A swim familiarisation training session planned for Saturday ahead of Monday’s mixed team relay was cancelled, with organisers wary of rain upstream in the last couple of days.

Two familiarisation sessions were also cancelled before last Wednesday’s individual triathlons.

The men’s race was also postponed from the previous day because of water pollution worries, a major story ahead of the Olympics.

But the strong current was the bigger issue, especially for the women’s race earlier in the morning.

Apart from the triathlon relay, the 10km open water swimming events for men and women are also scheduled to take place in the Seine next week.

France has made huge efforts over the years to improve the water quality of the Seine as a legacy project, investing more than one billion euros ($A1.7 billion).