In the first instance, 15 fishermen who had put out to sea from Puthenthoppu village near Thiruvanthapuram were rescued after their country craft capsized about 20 km off the hamlet.
Fishermen in other boats and coastal police helped rescue them, police said.
Four fishermen suffered minor injuries and were given first aid at a hospital in the capital city.
In the second incident, 17 fishermen from Thrissur district had a miraculous escape when their fibreglass boat capsized off Kochi coast at around 9.30 AM.
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The fishermen then jumped into the sea and held on to a 'trailor boat' attached to their vessel.
Marine Enforcement and Kochi coastal police rushed to the area, about four nautical miles away from Njarackal and rescued them after receiving an alert from fishermen in another boat, police said.
They were later taken to a government hospital and discharged after a mandatory check up.
The vessel and the net could not be recovered, police said.