Two of the country's premier waterways have been shut down with authorities blaming indiscriminate attacks on boaters and barges.
The Grand Canal and Royal Canal were closed indefinitely in Dublin at the end of September despite up to €50m being spent in recent years to encourage more traffic to flow.
Waterways Ireland blamed anti-social behaviour and warned of safety fears for its staff and boaters after cataloguing 28 incidents in four years including assault, intimidation, theft, vandalism and arson.
The shutdown was ordered after a gang of youths pelted a couple on a boat with rocks as they were being guided through the lock in Inchicore and blocked the boat from passing through.
The agency claimed its staff have been harassed and threatened elsewhere as they escort up to 70 boats a year through the capital.
Mick Kinahan, of the Dublin branch of the Inland Waterways Association of Ireland and an experienced guide on the Dublin canals, accused authorities of over-reacting.
"I would hate to see that because of a few incidents, some of them minor, that this approach is taken," he said.
"It's totally and utterly over the top. I would question the agenda."
Waterways Ireland began formally guiding boats in and out of Dublin on the canals in 2007 in order to keep users safe. Anyone wanting to use the routes has to give two days notice.
It said the worst incidents of anti-social behaviour generally occur between the first and sixth locks on the Grand Canal and during spells of good weather.
The incident in August, which is said to have sparked the closure order, involved a couple who wished to travel across Ireland by water, including passing through Dublin.
"The recently reported incident has been the most serious and required an appropriate response," a spokeswoman said.
"Presently a review is being conducted of the movement of boat in the area identified and the procedures in place.
"Waterways Ireland is taking this opportunity to undertake a review of the wider process, and when it is completed any appropriate updates will be put in place, aimed again at the safety of boaters and staff."
Waterways Ireland apologised for the closure of the canals but said it expected disruption to be limited as it does not have any current bookings for boats to be guided through the city.
Up to 70 barges and boats travel the route every year.
Mr Kinahan questioned whether Waterways Ireland were attempting to stop boats and barges getting access to the Grand Canal Basin amid concerns over permits and overcrowding at the city centre berths.
"Things are not as bad. These things happen in isolated areas," he said.
"Anti-social behaviour is going to take place anywhere in the country.
"I would speculate that they have used this to close the canals. They tried to stop people coming into Dublin and they can't. Maybe that was their way of saying the canals are closed and they could justify it. But I can't see how it is for health and safety grounds for these minimum number of incidents."