Once a year, I inadvertently overhear someone wondering aloud about the sea level while crossing the Mahim or Thane Creek bridges without realising that the sea has tides. Similar conversations are heard at the beaches too. The Bandra Worli Sea Link, which now features in almost every movie about Mumbai, as seen from Mahim. Pic: MS Gopal Not being aware of tides often leads to lovers being stranded on the rocks along the coast, or even people getting washed away by waves during the monsoons. People regularly throng the sea-fronts of Mumbai - sometimes the beaches, sometimes the promenades, but…