Or filling it with 618 gal of fuel...
Not a boating enthusiast, but I suspect a mere 600-gallon tank of diesel will only get you out for a weekend cruise and back. I read a blog by a couple who moved from a big custom motorhome with a 300-gal fuel tank to a recreational trawler with 10X the fuel capacity. Here's their description of the boat:
The boat is a one-off custom build, a steel hull and aluminum superstructure, completed in 2003. She's 52' long, 15' wide, and displaces (weighs) 85,000-100,000 pounds, with a tonnage of 66 Gross, 52 Net Registered Tons. She's propelled by a single 300 horsepower diesel driving a conventional propeller and shaft ahead of a skeg-hung rudder. A bow thruster allows for easy maneuvering of the single-screw boat at the dock, and hydraulic active-fin stabilizers minimize rolling at sea. With 47.5 feet to the waterline and a full-displacement hull, she has an absolute top speed of 10 knots (11.5 mph), and a cruise speed of 8 knots. With 3,300 gallons of diesel fuel, her range at 7 knots is better than 6,000 nautical miles, more than enough to cross the Atlantic or Pacific oceans.
They did not disclose the purchase price, but I have seen trawlers of the same size but newer going for less than $500K. What impressed me most when reading the above blog was the amount of work he put into it next to fix things up. Some were pretty major, such as emptying and repairing the cavernous fuel tanks.
I think I'd rather go back to work. It would be less stress and physical labor, and they even pay me for it. How 'bout that?