Ocean tides occur because the water flows from locations with a low tide to those with a high tide on the other side of the world. On the other hand, the world’s lakes are not interconnected, & therefore, no significant tides can occur.
Tides are much smaller in lakes, and flat-Earthers use them to discredit gravity. In reality, lakes are not connected. Water in a lake cannot flow to another on the other side of Earth and cannot cause a low tide to one & high tide to another.
When a location on the ocean has a high tide, the volume of water increases and this additional volume of water comes from where a low tide occurs. In lakes, it cannot happen. While the Moon has practically the same influence, an additional volume of water cannot flow in and cannot cause a meaningful tide.
The same thing happens to other bodies of water, including rivers, ponds, pools, etc. A meaningful tide cannot occur because water cannot flow freely from or to another location having the opposite tide on the other side of the world.
Smaller tides are measurable on big lakes. The Great Lakes’ tides are less than 5 cm and are masked by other factors. As a result, even the Great Lakes are considered non-tidal for practical purposes.
Reference
- Tide – FlatEarth.ws
- Do the Great Lakes have tides? – NOAA