Basking sharks pose no threat to humans
A new database has been set up to log sightings of sharks around the coast of Devon and Cornwall.
The Shark Trust says it is vital sightings are reported to help it ascertain the number of creatures being trapped in fishing nets.
It follows the discovery of a dead 4m (12.5ft) long basking shark entangled in nets at the River Avon estuary, near Bigbury in Devon on Monday.
The trust is offering boat owners advice on how to behave around sharks.
A code of conduct has been established to prevent the creatures being injured.
This includes vessels turning their engines to neutral if they are within 100m (328ft) of a shark.
The basking shark is the most common species to visit the South West coast in the summer months to feed on plankton when sea temperatures rise.
They do not pose a risk to humans, but can grow up to 12m (39ft) in length and weigh up to 7 tonnes.