As planned, the solar-powered SeaCharger entered Californian water on May 30, but didn't get very far. A software bug forced the attempt to be abandoned. A couple of weeks later, though, and the 8-foot long craft was on its way again. And just over 41 days after relaunch, it arrived safely at Mahukona, Hawaii.

The aim of the project was to create an unmanned surface vehicle that could cross an ocean using sunlight as its sole energy source. The SeaCharger has a fiberglass-covered foam hull topped by two photovoltaic panels charging a LiFePo4 battery bank housed within a thruster pod suspended beneath the craft. A watertight pod between the solar panels is home to an Arduino-based autopilot, GPS and satellite modem circuitry.

McMillan relaunched the 91-inch long SeaCharger from Half Moon Bay in California on June 11. It managed an average speed of 2.11 knots (2.43 mph) and covered around 58 miles (94 km) per day. Wind and currents did push it around a little on its journey, but after 41.4 days on the water and clocking up 2,413 miles in total, it arrived safely in Hawaii on July 22.