The yearly project is intended for those who cannot afford to travel during Holy Week and will include 12 pools near a boardwalk in the capital of Santo Domingo.
Critics say the project should have been cancelled since there is currently water rationing and interruptions in water service.
Mayor Roberto Salcedo said on Wednesday that water for the pools will come from underground reservoirs his office uses. He estimates 500 000 people will visit the artificial beach.
Santo Domingo has 30km of coast, but the beaches are mostly rocky and the water contaminated.
The capital's lone sandy beach is closed during Holy Week because its waters are considered too dangerous for the holiday crowds.