For the summary, I should mention the key elements: Paris reopening the River Seine, public swimming after 100 years, three sites, capacity, water quality efforts, and the connection to the Olympics. Also, the time frame until August 31 is important.

Now, the SEO headline. The goal is to make it attention-grabbing and include relevant keywords. The main topics here are “Paris”, “River Seine”, “swimming”, “public”, “reopened”, and “Olympics”. Maybe something like “Paris Reopens River Seine for Public Swimming After Century-Long Closure, Thanks to Olympics Efforts”. That includes the city, river name, action, and the motivation (Olympics). Also, including “Century-Long Closure” adds a wow factor. The headline should be under 70 characters, but let me check. Let me count: “Paris Reopens River Seine for Public Swimming After Century-Long Closure, Thanks to Olympics Efforts” — that’s around 80 characters. Maybe slightly long, but search engines usually allow up to 70. Hmm. Maybe shorten to “Paris Reopens River Seine for Public Swimming After 100 Years, Olympics Boost”. That’s better. Using “100 Years” instead of “Century-Long” saves characters. Also, “Olympics Boost” adds the connection. Let me count again: “Paris Reopens River Seine for Public Swimming After 100 Years, Olympics Boost” — about 70 characters. Yes, that should fit. The important keywords are there: Paris, River Seine, public swimming, 100 years, Olympics. That should help with SEO.
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Paris Reopens River Seine for Public Swimming After 100 Years, Olympics Boost

After nearly a century, Paris has reopened the River Seine for public swimming, offering three sites with capacity for over 1,000 daily swimmers through August 31. Extensive water quality improvements driven by Olympic efforts make this summer debut possible.