Pool Experts Say Lincoln Memorial Reflecting Pool Damage Wasn't Vandalism

President Trump's explanation for fresh damage at the recently renovated Lincoln Memorial Reflecting Pool isn't holding water ... 'cause two pool experts tell TMZ this doesn't look like the work of vandals.

Take the plunge and watch our "TMZ Live" debate ... an anonymous pool surfacing expert and veteran pool consultant Rudy Stankowitz joined us to break down what they believe really caused the mess ... and both say the problem likely started during construction.

Trump says vandals are to blame ... but both experts told us the problem looks self-inflicted. They pointed to installation issues -- not sabotage -- as the likely cause.

The anonymous expert told us the coating appears to have never properly bonded to the pool's surface ... while Stankowitz believes crews may have missed a critical recoating window during the project -- two different paths to the same conclusion.

The controversy has put the Reflecting Pool's reported $16M restoration project under a microscope.

In recent days, the project has generated headlines over algae concerns, dead ducks floating in the water, POTUS' vandalism allegations, and a string of arrests around the iconic landmark -- including a former Olympian.

Our intrepid TMZ DC producer Jacob tried to follow Trump's trail himself ... calling and then showing up at the National Park Service after Trump said officials there could prove the vandalism claim -- but Jacob couldn't get anyone to back it up.