Video report by ITV Granada Reports correspondent Joshua Stokes.
The number of basking shark sightings recorded in the Isle of Man has been decreasing year-on-year, according to the Manx Basking Shark Watch group (MBSW).
This year there has been a total of just nine basking sharks recorded in Manx waters compared to a few hundred spotted in previous years.
Basking sharks would usually be seen around the south west of the Isle of Man, as this is where the majority of plankton can be found for them to eat.
Between 2005 to 2013, hundreds of sharks used to be spotted around the Island arriving in mid-May and leaving by the start of August.
MANX BASKING SHARK WATCH THEORIES
Jackie and Graham Hall have been running the Manx Basking Shark Watch for over 15 years, spotting and tracking basking sharks around the Isle of Man.
They have three potential theories to why the number of sightings has decreased.Natural Variation - there have always been times when little to no sharks were spotted in the Isle of Man. The sharks may choose to go in a different direction during their migration. How much of the gulf stream intrudes onto the Irish Sea can also have an effect.
Climate Change - the sea around the Isle of Man is warmer than it used to be and if the temperature is not right then the plankton that basking sharks eat will not be in Manx waters.
Man-made Interference - the number of wind farms in the sea have caused an increased amount of silt which may alter a basking shark's path. More trawling and general boat activity may also have an impact.
They also say it may be a combination of all three put together.
When asked about the Manx Basking Shark Watch, Jackie described it as "one of the biggest privileges of our life" and both say they hope the sharks will make a return to the Island.
The team at MBSW have had to acquire a license from the Isle of Man Department of Environment, Food and Agriculture (DEFA) to be allowed to conduct the scientific work over the years.
More on the Manx Basking Shark Watch can be found here.