Scotland is this year's top spot for basking sharks, according to the results of a UK-wide survey.
A total of 120 sharks were sighted over a 10-week period, 106 of them in Scottish waters. This compares to only 40 sightings in Scotland last year.
Marine conservationist Colin Speedie said the cause of the rise might be currents pushing plankton north.
The figures were compiled by The Wildlife Trust's Basking Shark Project for 2004.
Mr Speedie said: "What is also interesting this year is that the areas which seem really rich in marine life are those within the proposed area for Scotland's first marine national park.
"We have also seen quite a few repeat sightings suggesting the sharks are returning to original sites because of the abundance of food."
The survey covers the waters of the English Channel, the Irish Sea, the Firth of Clyde and the Hebrides.
The Scottish Wildlife Trust (SWT) said the number of boat operators taking visitors to see marine wildlife had increased by 79% since 1997.
The SWT and WWF Scotland have joined forces to promote the protection of species like the basking shark through the Joint Marine Programme.
Dr Rebecca Boyd, of the programme, said the two organisations supported the establishment of a marine national park.
"We believe this is an excellent way of giving coastal communities lasting economic support while allowing our unique wildlife to flourish," she added.
"A marine park would allow better planning of activities like fisheries, aquaculture and marine tourism, avoiding damaging competition between user groups for space and resources."
Scotland has two terrestrial national parks but no marine ones.
"Hot spots" already identified include the area around Land's End, the Lizard Peninsula and the waters off Plymouth in the south west; the Isle of Man; Strangford Lough; the isle of Arran; and the Hebrides.
Recent studies by Cefas (the UK's Centre for Environment, Fisheries and Aquaculture Science) using satellite tags have shown the sharks tend to move out to deeper water outside the summer months, when they are most likely to be seen close inshore.
The sharks are protected within UK territorial waters, though some of the legislation does not cover Scottish and Northern Irish waters.