The answer to this question is ‘it depends’. It depends on the quality you want to buy and what you want to use it for. There are swivel tables that are made of materials that are waterproof because some people want to use them while taking a bath or, in some situations, like with seniors who have mobility problems, some liquids might be spilled on the tray.
The ideal swivel table is waterproof, but if you find one that you like a lot and is not waterproof, it is not hard to cover it with a water-resistant material or apply a water-resistant paint to make it suit your needs. However, this involves some extra work that can be compensated with buying one that already has this feature.
High-quality swivel tables are waterproof and can be used anytime and anywhere for long periods because they are made of high-quality materials that do not deteriorate over time.