Speedboats and jet skis could be allowed to travel closer to the shoreline at popular beaches.
At present, vessels are banned within 200m of the low water mark at Brighton, while the limit at Hove is 500m.
But as part of a revision of pleasure boat bylaws being considered by Brighton and Hove City Council, there are moves to bring Hove into line with Brighton.
Swimmers fear there could be an accident if boats are allowed to come closer to the shore.
But the council says there is a need for consistency as the 500m limit off Hove is difficult to enforce and is regularly flouted.
Officials are consulting with interested parties, such as Brighton Marina, speedboat owners and the Brighton Swimming Club, whose members swim all year round from their base at Kings Road Arches.
The original bylaws banning speedboats from within 200m of the low water mark at Brighton were introduced in 1976 after an accident off Hove in 1973 when a swimmer had his arm severed by a speedboat.
A new 200m limit from Saltdean to Hove would be broken by channels allowing boats to come ashore at Saltdean, Rottingdean, Brighton Marina, the Banjo Groyne opposite the old Peter Pan's playground, either side of the Palace Pier and opposite Wish Road, Hove.
The Brighton Swimming Club wants the limit extended to at least 300m, which would take it past the ends of both piers and prevent speedboats going under the northern tips of the structures.
Henry Law, of the swimming club, said: "We are involved in consultations with the council at the moment and we are confident our concerns can be resolved.
"We want to ensure the agreed limit and the channels are marked off by proper buoys.
"The current inflatable buoys keep coming adrift. They should be properly chained to the seabed.
"I am also concerned an accident is waiting to happen off Brighton in the evenings because speedboats and jet skiers know the patrol boat goes off duty at 5.30pm and they can do anything they want."
Paul Elgood, leader of the Liberal Democrat group on Brighton and Hove City Council, wants Brighton brought into line with Hove's 500m limit rather than the other way round.
He said: "A 500m limit properly patrolled would make things far safer for those who go into the water off Brighton and Hove. A lot of swimmers go out more than 200m from the shore.
"Letting boats come closer will increase the chances of accidents."
Sebastian Rouse, who runs Hove Lagoon Watersports, said: "There is a need for standardisation of the limit. As long as we have an access channel for our safety boat, I have no problems with a 200m or 300m limit."
A council spokeswoman said: "We are involved in consultations with interested parties about the need to standardise the pleasure boat bylaws.
"We want to have a straight line across the sea where it is known boats cannot venture except through specially-marked channels and where swimmers know they are safe from boats.
"We would like the new bylaws to be in force for next year's holiday season."
Brighton Council was forced to introduce regulations restricting speedboats from coming too close to shore after Michael Lade, then 24, lost his arm in a collision with a speedboat in June 1973 as he swam 50 yards off the beach.
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