Many sharks turn up injured
Anyone harming basking sharks off the Isle of Man coast could be fined up to £5,000, the government has warned.
About 200 sightings have already been reported around the island since the start of the summer season.
Now the government is urging people to read their code of conduct for watching marine wildlife after a number were injured in boat collisions.
Anyone who witnesses the animals being harassed should contact conservation officers, the government said.
The Department for Agriculture, Fisheries and Forestry (DAFF) said it had received a number of photographs of badly injured sharks.
Basking sharks can grow to more than 30ft (10m) long and are the second biggest fish in the world.
They are one of the Isle of Man's best known protected species but are easily disturbed, DAFF said.
"As the Isle of Man is a hotspot for these amazing creatures, the Manx Government and the island's population have a special responsibility for protecting them," said a spokesperson.
"Basking sharks are protected under the 1990 Wildlife Act and it is an offence to intentionally kill, injure or recklessly disturb a basking shark and fines of up to £5,000 can be applied.
"To help reduce the possibility of people harming marine wildlife there are codes of conduct available from the Wildlife and Conservation Division of DAFF."