Anything modified by Towers means a hotel within the hotel on the top floors with its own more exclusive and nicer lounge with a view. IIRC this property has a regular Sheraton club lounge on a low floor without a view. The Harbor View suites might have a full view of the harbor, but you would not have access to the Towers lounge. OTOH, I believe that there are some Towers suites with side rather than full harbor views; there might also be suites on the back of the hotel without water views.

Rules say that you don't get an upgrade to a Towers room or Towers suite unless you pay a Towers rate.