The engines that power most of the country's small leisure boats are being banned - leaving owners facing huge bills to replace them.
The National Transport Authority will no longer give permits for two-stroke outboard engines from December, saying they cause significantly more noise and pollution than four-stroke counterparts.
Boats that are already registered and licensed will be allowed to remain in use until the end of 2016, then they will need new engines.
The authority originally gave owners until July this year to ditch their two-stroke engines, but in March extended the deadline to December. The new rules do not affect commercial vessels.
Many owners and operators remain unaware of the change, however. Tony Hajj, a team administrator for X-Ventures, a tours company in Abu Dhabi, called for clarity.
"I've been hearing about this rule for the last three years and they keep changing the dates," he said. "There has to be an official announcement clarifying the rules on these engines."
He agreed that the old polluting two-stroke engines should be restricted for the good of the marine environment, but "the first thing they should do is stop the vendors from selling them".
"This shouldn't be the first priority for regulators," he added. "We need to clean the waters in this part of the world - there is far too much trash is the sea, that is harming the environment."
Mr Hajj runs a boat with a newer "eco-friendly" two-stroke engine that differs from older variants by trading power for fuel-efficiency.
"Normal two-stroke engines create a lot of smoke and noise and use a lot of oil. This one does not," he said.
It is not clear whether the newer, cleaner engines will also be banned, or if the ban will extend to other vehicles, such as a Jet Ski, which are less tightly regulated.
Some marinas already ban two-stroke engines. Dubai Marina Motor Yacht Club barred them from its waterways in 2006, citing serious environmental concerns.
The engines commonly leak small amounts of toxic oil into the water, which can cause significant harm to marine wildlife, and the fumes released are damaging to the atmosphere.
Worldwide, many ports or marinas also restrict their operation, particularly in parts of the US, to meet environmental and noise pollution standards.
Most larger ships and cars use four-stroke engines, which are more fuel efficient. But in general, smaller boats, motorcycles and scooters are fitted with cheaper, simpler two-strokes.
Some owners are worried about the impact of a blanket ban on the boating community.
Steve O'Brien, an Abu Dhabi resident who owns a boat with one of the newer, low-emission two-stroke outboard motors, said the impact on private boat owners would be "huge".
"I can imagine the impact on the numerous marinas in the UAE will equally huge," he said. "It will cost anywhere from Dh80,000 up to replace two-stroke engines with new four-stroke ones and I can imagine that … the suppliers will probably push their prices up because there will be a high demand for four-stroke engines."
He cautioned that "this new ruling could well kill the pleasure craft industry in the UAE completely".