Anything that reduces waves makes a pool faster. This includes deeper, good lane lanes, good gutters, etc.
15 seconds/100m is way larger than the difference between a slow and fast pool though (unless you swim 10 minute 100s).
All true. However just thinking of a normal pool depth, lets say 4’, any surface waves would be considered a “deep water wave” in ocean dynamics. The difference in swimming in a 4’ pool and a 25’ lake would not make a difference due to the height/magnitude of the waves you put off. This would make the effect from the bottom pretty much nothing. However, the effects from the walls and lane ropes would cause some resistance being how the distance between you and these objects would be “shallower.” Basically what I’m saying is it only the walls and objects on the surface that would possibly have some effect.