The tech billionaires aren’t just grabbing trophy Florida mansions—they have competing half-billion-dollar megayachts jostling for dock space

In early December, Miami’s glittering skyline was disrupted by a gleaming 466-foot vessel pulling into its harbor. Sergey Brin, a Google cofounder, had decided to make a stop in style for the city’s Art Basel fair, arriving in a superyacht called Dragonfly.

Miami and its nearby coastal enclaves are fast becoming the staging ground for Silicon Valley’s grandest displays of wealth, and the showmanship is extending from seaside mansions to hulking yacht berths. 

Over the past few years...