Where the hell am I gonna be that I would spot one of these monster yachts?

The Web site yachtspotter.com has in recent months become the nautical answer to Gawker Stalker, with boating enthusiasts around the planet posting daily sightings and precise locations of the world's biggest privately owned vessels.

Want to know where Oracle software-company founder Larry Ellison and his 454-foot Rising Sun -- the world's longest yacht under private ownership -- have been cruising lately?

Yachtspotter puts the 188-foot Ultima III, owned by MacAndrews & Forbes billionaire Ronald Perelman, in Antibes on May 26.

Boating spies can barely keep up with Microsoft co-founder Paul Allen, because he has two mega-yachts wandering the globe: the 413-foot Octopus, (seen above), boasting a crew of 57 and the 303-foot Tatoosh (outfitted with a swimming pool and two helipads). Yachtspotter reports that Octopus has been in Australia for the past month, most recently anchored off Exmouth on June 1, after stopping off in Tahiti on March 15. Tatoosh, meanwhile, sailed into the Mediterranean on May 15 after an April 30 stop in New Orleans capped a cruise of the Caribbean.

Bill Gates' 299-footer, Ice, spent May mainly in Spain. Yachtspotter found it in Malaga on May 8 and Barcelona on May 16. Software mogul -- and Martha Stewart toyboy -- Charles Simonyi took his 231-footer, Skat, to Venice on April 10, Croatia on April 26 and the Riviera's Cap Ferrat on May 17. Calls to Microsoft, Oracle and Simonyi were not returned.