A number of traders are battling to stay open despite the deluge, which came after the wettest December on record.
And the rainy trend shows no sign of letting up, with showers forecast every day till early next week.
"We're still open but nobody can get in to us," said David Cochrane of Custom Covers NI, who is keeping his new Kinnego Marina unit open despite five inches of flood waters.
"It's a bit of a mess to say the least. The financial side of it has cost me a lot."
Yesterday BBC NI weatherman Barra Best posted video of the damaging flooding at the marina on the southern end of Ireland's largest lake.