The atmosphere for Olympic swimming is electrifying.

The times?

Not so much.

Through the first four days of competition in the portable pool at La Defense Arena, no world records were set.

That finally changed in the final race Wednesday night when Pan Zhanle of China broke his own mark in the men’s 100-meter freestyle. Still, most of the best swimmers in the world are clocking slower-than-expected times.

The culprit appears to be a pool that is slightly shallower than the optimal depth, which allows a couple of extra rows of prime deck-side seats to remain in use but creates more waves and turbulence rolling up to the surface.