An Taisce has expressed concern that moorings proposed by Waterways Ireland at a location on the Shannon at Portumna will affect the scenic view and detract from the town's historic bridge over the river.
The environmental agency has also warned the development could result in boat collisions involving inexperienced cruiser-hire holidaymakers who congregate in the area during the summer months.
Waterways Ireland is seeking permission from North Tipperary County Council to install 60m (200ft) of floating moorings downstream of the bridge, along with the development of a 20m (65ft) floating breakwater upstream and a 33m(108ft) timber walkway from the bridge.
An Taisce says the bridge, which opens to allow large boats through, is almost untouched since it was built in 1911. Yet the planning application provided no assessment of the visual impact of "grafting on a modern floating jetty to an important part of Ireland's transport heritage".
The agency adds that the moorings would introduce "a jarring note" right in the centre of the river on the notable view downstream of the bridge.
It says the main objective of the Western Area Local Development Plan - which the council introduced to protect the north Tipperary stretch of the Shannon - was to enhance the existing strong visual character of the area.
"In our opinion, this application, which seeks to place an effective obstacle in the middle of the boat-stream, needs further consideration from a health and safety aspect."
The agency says that area of the river is very busy during summer. Large numbers of inexperienced boat-renters face the task of making their way through the confines imposed by the bridge. "To restrict their room to manoeuvre so close to the bridge may unnecessarily increase the risk of collisions," An Taisce warns.
North Tipperary County Council says it will not make any decision on the planning application until it receives further information.