Waiters, bar attendants, room attendants - they're the usual nominees when crew members are credited with making a cruise enjoyable.
Yet there's a small army working below deck, as it were, with equally vital roles to play in ensuring passengers enjoy their holiday. Most are invisible.
Pavo Brzica has 50 under his command on Radiance of the Seas and if things are going well, chances are the cruisers won't see any of them during their voyage. But then who of them wants to see a plumber on holiday . . . except when the toilet in their cabin is blocked and suddenly knowing that one's in the vicinity is a godsend.
Mr Brzica, 44, hails from Dubrovnik, Croatia, and still lives there when not at sea. While cruising, looking after the needs of some 2500 passengers (and 850 crew) is a seven-day- a-week job, equivalent to overseeing the services for a small town.
To cope, he works a 10-weeks- on, 10-weeks-off shift. "You couldn't do it for any longer," he says of his work shift. He points to the mobile phone attached to his belt: "This never stops."
As the ship's chief engineer, Mr Brzica's workforce includes electrical engineers, refrigeration specialists, navigational experts, electronics engineers and welders. Anything and everything concerning the electrics, refrigeration, power and, yes, plumbing (there are five plumbers on board) comes under his purview. That jurisdiction includes new technology like the internet; there are seven IT specialists on Radiance's crew of 850.
Mr Brzica's career at sea started in 1992, and he entered the cruise industry seven years later, joining the Royal Caribbean International fleet, of which Radiance of the Seas is a member, in 2002.
He's responsible for ensuring the 300m-long ship has sufficient power to traverse the world's oceans. Two General Electric gas turbines (the same that power DC10 airplanes) produce 25MW and comprise the ship's main source of power, but there's also a 9.5MW steam turbine that runs on the heat out of the engine exhaust and a V16 diesel engine.
Because the gas turbines are environmentally cleaner and produce far fewer emissions than diesel engines, Radiance of the Seas is regarded as a "green" ship and Royal Caribbean also operates an environmental protection program called Save the Waves, which it began in 1992. This program's guiding principles are to reduce the generation of waste produce, recycle as much as possible and ensure the proper disposal of waste, and passengers will spot stickers promoting Save the Waves around the ship.
Although its tanks can carry 2500 tonnes of drinking water, it has a reverse osmosis unit capable of making potable water.
A ship of such size, of course, with 3000- plus passengers and crew on board, creates a lot of waste - 500- 600 tonnes a day. Solid waste is incinerated or disposed of on land; food waste is pulped and discharged at sea; and aluminium cans, glass and the like are stored and recycled.
Mr Brzica insists Royal Caribbean goes "above and beyond" the environmental standards required by regulatory authorities, and explains the onboard processes used on "black water" from toilets and greywater from showers. Faecal waste is macerated, pulped and subjected to UV rays to eliminate bacteria; by the end of the treatments, the waste is so clean it can be dumped in the waters of such ports as Alaska's Juneau. And Alaskan laws on waste disposal at sea, Mr Brzica notes, are stricter than international regulations.
But RCC cruise ships don't release their effluent in ports. He explains the company policy is for its ships to take such waste 12 nautical miles out to sea before releasing it. It helps that the ship has enough waste storage space aboard to go nine days without needing to offload waste, which is useful when it traverses the pristine waters off Alaska.
The environmental policies are admirable, and have been recognised with a number of awards. The commitment is commendable because it contrasts with the company's unhappy history. In 1998 and 1999, Royal Caribbean International pleaded guilty to charges of dumping waste oil, dry-cleaning fluids and photo- developing chemicals into the waters of the Caribbean, the Inside Passage, Miami, Puerto Rico, the American Virgin Islands and New York Harbour. According to the US Department of Justice, Royal Caribbean was fined $27 million after a five-year investigation which included charges that "the company engaged in a fleet-wide conspiracy to dump oil into US coastal waters and lied to the US Coast Guard to cover up the crimes by falsifying oil logs".
The company's then president, Jack Williams, apologised for the pollution and for trying to conceal it and several high-level managers were reportedly replaced, as Royal Caribbean set out to restore its reputation. Today, a fair amount of space on Royal Caribbean's website is allocated to promoting its green credentials, with chairman and CEO Richard Fain committing his company to a philosophy of social responsibility and environmental protection.
"We at Royal Caribbean International know we have a special responsibility to protect our marine ecosystems," he writes. "Clean oceans are good for the environment, good for our guests and good for our business.
It keeps Pavo Brzica busy, too.
It helps that the ship has enough waste storage space aboard to go nine days without needing to offload waste, which is useful when it traverses the pristine waters off Alaska.