Newtons simplified explanation of the tides clearly showed how the gravitational forces act upon the tide. However, it quickly came under scrutiny because it did not explain what actually occurring on Earth.
The reality of the tides is made complicated by a number of factors. The tide is constantly dragged across bottom of the ocean by the moon and the sun. Large landmasses get in the way of a continuous tide and rebound the wave, causing interference. The force of the wave squeeze the tide through narrow straights and channels, drastically altering the shape and timing. All these circumstances combine to create radically different tidal conditions across the coasts of the world.
In some place, like much of Europe, the tide follow the Newtonian laws perfectly, occurring 2 times a day and coming in 50 minutes later each day. In other place, there is a single tide in a day or 4 tides instead of the typical two. These complexities and differences in tides across the world present a challenge for scientists even today.