Eric Kvaalen Les Essarts-le-Roi, France The Sea of Japan has almost no tides, but I suppose they are still detectable. This sea doesn’t have a natural oscillation period related to any lunar or solar period, and is fairly cut off from the ocean, which explains why the tides are small. Advertisement Stephen Rowe Shepperton, Middlesex, UK In my early career, I worked in the ship division of the UK’s National Physical Laboratory. The facilities included a massive indoor towing tank (sadly long since demolished to make way for a superstore). This tank was 400 metres long, almost 8 metres deep and contained more than 45 million litres of water.