Polish practice 8+8 Concept Studio has released images of a proposed underwater tennis court planned to be built off the coast of Dubai. Staged beneath an expansive glass roof that would put marine life on display, the radical proposal is being called into question as engineers debate its feasibility. As the Daily Mail reports, the scheme seems unlikely due to the challenges of manufacturing glass sheets large enough to span a tennis court and ensure that the structure is impact resistant. Refracting light is also a valid concern.