Safe Bathing Enclosures for Open Coasts: Structural Loads, Current Exchange and Capacity Budgets for a Netted Swimming Enclosure

Many tropical and subtropical beaches are effectively closed to safe swimming by drowning hazards, marine stingers and shark risk. This paper originates a parametric design for a modular 100 m by 50 m netted bathing enclosure (200 m of net, 5,000 m2 protected surface, 7,500 m3 enclosed volume, 450 m2 of net curtain) and computes four budgets from stated assumptions: hydrodynamic drag and anchor tensions across currents and wave climates including biofouling growth over a 90-day cleaning interval; water exchange and a slack-water residence bound of about 9.3 h; bather capacity of 350 at a comfortable 10 m2 per bather; and cost per protected bather-day of $0.61-$2.15 from a capital cost of $175,250. SIMULATED, NOT MEASURED: no enclosure described has been built, installed, or swum in. Failure modes are stated plainly: no storm rating beyond the screened limits, entrapment and entanglement risk, and no protection outside the perimeter.