When staff built a striped tent covering the water taxi dock of the Aman Hotel in Venice, largely hiding the guests arriving for Jeff Bezos’ wedding, it was just another insult to the many sweaty photographers who had been trying to cover an event that has been guarded with a stubborn veil of secrecy.

“Did Bezos arrive yet?” one reporter shouted on Wednesday as she slipped by on a water taxi called “Confusion.”

Nobody knew.

Since their relationship became public six years ago, Ms. Sánchez and Mr. Bezos have seemed to enjoy the limelight. Their romance was on display at Wimbledon, at President Trump’s second inauguration, at countless dinners and galas and in the glossy pages of gossip magazines.

And on Thursday, a roster of celebrities began to hit the town as the first of the weekend’s festivities began, with guests like Tom Brady, Leonardo DiCaprio, Orlando Bloom, Oprah Winfrey and a raft of Kardashians stepping gingerly into motorboats, careful of their finery. The bride herself wore an embroidered, off-the-shoulder dress by Schiaparelli to a Thursday night event at the Madonna dell’Orto complex, which includes a Renaissance-era church.

Yet, much about the wedding, in one of the world’s most photographed cities, was being obscured even as the big weekend begins.

It was even unclear whether the couple would technically be married in Venice, or if they would just celebrate their wedding in the city. Until few days ago, the dates were not certain. And even at the most-discussed locations, staffers said they had not been told whose event they were preparing for.