Slaughter cows, drown others before ferries can ply the Mtongwe crossing channel, Mijikenda elders said on Tuesday.
They maintained that there is a risk of repeat disasters if the channel, infamous for the 1994 tragedy that left 272 dead, is not cleansed.
The elders said that the route 'has a bad omen', hence the need for traditional rituals - locally know as Tambiko; to make it safe for use.
They said that the dark spirits which caused the said accident are still yearning for more blood.
"This can be avoided if we 'pray and offer cows to the gods'," the elders said.
Mijikenda traditions dictate that the slaughtered animals are eaten at the site of the ritual and no meat is taken home.
Kenya Ferry Service reportedly bought three cows during the official relaunch of the channel on Monday.
The function was attended by President Uhuru Kenyatta and Deputy President William Ruto among other coast leaders.
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But Likoni MP Masoud Mwahima said the cows slaughtered at the fete were not meant for traditional celebrations.
"We slaughtered the animals just to celebrate the reopening of the channel which had been closed for over 5 years," Mwahima said.
Rashid Kombe, who escaped the April 1994 tragedy, said the ocean gods must be appeased before the ferry resumes operations.
He urged Kenya Ferry Service not to take chances with lives of those who will use the ferry.
"I know the world has changed and people no longer believe in such traditions. But for us as Mijikendas, we still hold to them," Kombe said.
However, Jonathan Katana said KFS should only conduct prayers led by religious leaders.
"We need to pray so that God spares us from any accident or tragedy. Religious leaders will intercede on behalf of everyone who will use the ferry," he added.