By Mark Kinver
Science and nature reporter, BBC News
IFAW'S SONG OF THE WHALE
Crew: 10 or 11
Weight: 65 tonnes
Length: 21.5m (70.5ft)
Engine: 370 horsepower
Moored in St Katharine's Dock, in the shadow of London's Tower Bridge, the International Fund for Animal Welfare's (Ifaw) research vessel, Song of the Whale, is taking advantage of a rare break from the open seas.
It is the first time that the boat has returned to her home port since being launched in 2004 by actor Pierce Brosnan and his wife.
Skipper Richard McLanaghan is using the time to carry out maintenance, such as the installation of porpoise tracking equipment, before departing the sheltered surroundings of the dock and embarking on the next voyage.
"In the 20 years we have been operating, we have visited more than 25 countries," Mr McLanaghan says.
This is the second Song of the Whale. The first was a converted 14-metre (46ft) luxury yacht, and clocked up more than 400,000km (250,000 miles) between 1987 and 2003.
But the combination of up to eight people on board, as well as food, communication and scientific equipment, meant conditions were very cramped, especially on longer trips.
The latest vessel, primarily powered by sail, has been designed especially for the tasks of researching the movement and behaviour of marine mammals, particularly whales.
The engine room has been sound-proofed to reduce noise interference
"When we built this boat, we put a lot of effort into making the engine and generator systems as quiet as possible," Mr McLanaghan explains.
"We have a specially designed propeller that is much more like a submarine's; the engine and generator are on very soft rubber mounts, and there is a lot of sound insulation around the engine room.
"We try to sail for as much of the time as possible in order to reduce the amount of noise we are making."
The reason for this is the crew's expertise in acoustics - in other words, listening to whales.
"We use the sound whales make to find them and count them," he says. "There are not many other people who can do this, [so] we are adding another string to the knowledge that already exists."
Traditionally, whales have been counted by ships steaming back and forth along a straight-line course with observers on deck.
However, these counts have had a high degree of uncertainty because the creatures spend much of their time underwater.
Using their acoustic expertise, the crew are going to spend the summer counting sperm whales in the Mediterranean Sea.
"We will come up with a baseline figure for sperm whales in the different regions of the Mediterranean," the skipper reveals.
"People will not be really able to say whether the numbers are up or down because no-one really knows how many they are in the first place.
"But we know that sperm whales are threatened in the Med because there are problems of them getting tangled in fishing gear, getting struck by ships, and pollution."
To carry out the count, the crew will use the vessel's hydrophone arrays. These devices consist of two microphones three metres apart at the end of 200m (656ft) of cable, and are able to detect whales up to 20 miles (32km) away.
"Using quite sophisticated software that we have developed, we are able to count them automatically, whereas in the past we have had to sit with headphones on and manually count them," Mr McLanaghan recalls.
As well as the count, he says the team will also photograph the whales' tails in order to identify them, and collect skin samples.
"Because we are an animal welfare organisation, we develop and promote benign and non-invasive research techniques.
"Part of the reason behind this is because you have got some nations, Japan for example, conducting scientific whaling. We are trying to demonstrate that you can carry out very good science without harming the animals."
To overcome the problem of collecting a skin sample without physically touching the whale, Mr McLanaghan explains that the mammals shed skin as they swim along, and leave a slick when they dive.
"So when they dive, we remain about 100m (328ft) behind them, and as soon as they disappear we position the boat alongside the slick and a couple of people enter the water with nets to scoop up bits of skin, which are then placed in test tubes.
"So we get samples without ever having to touch the whales."
During the summer count, the Song of the Whale crew will be complemented by researchers from nations participating in the research.
While onboard, they will be trained to use the techniques needed to carry out the survey, Mr McLanaghan says.
"So when a big, multi-vessel survey takes place, there will already be a number of people from those countries that will be familiar with the system."