code: function isSea(lat, lng) {
    if (landLookup === null) {
      const map = getMap();
      landLookup = new GeoJsonLookup(map);
    }
  
    return landLookup.hasContainers({type: 'Point', coordinates: [lng, lat]});
  }
docs: Returns wheather the given point is in the sea or not.
  @public
  @param {number} lat  The latitude of the point.
  @param {number} lng  The longitude of the point.
  @return {boolean} True if the point is in the sea, false otherwise.