Can this pond be sealed?

I'm trying to wrap my head around my pond, which doesn't hold water well. There's a seasonal creek that flows, as well as seepage coming in from 2 directions. If waters coming in from seepage, wouldn't that water
flow push out any clay that is sealing the pond?  It seems in this situation it's dependent on the flow coming in, cause when the flow stops, it creates leakage out the same way the water was coming.

Am I making sense?

Clay would seal water movement, regardless of direction.  If water is seeping in, then it can seep right back out.
Sounds like there isn't enough clay.

Think of a small pinhole in A bucket. The bucket is full of water.  You could place a piece of saran wrap over the hole (From inside the bucket) and the water would press it against the hole. Place it on the outside and it would fall or get blown out by the water.

Does the same thing happen with clay? In one direction the clay is pushed against the dirt underneath,  but the other direction (underground seepage into tne pond), the clay is pushed away,  like the outside of the bucket.

Depends on the reason for seepage, and what other routes the water has. Once you have a full pond pushing on a clay layer, it can prevent the seeping water from pushing into the pond. This depends on the pressure of the seeping water. If it can go in other directions it probably does not have much pressure.

If it does not hold water than you need either a liner or clay to seal it. If you are thinking of clay, speak to a professional that does this kind of work.