It is believed that the effect of barometric pressure is greater in shallow water than deep, probably due to the pressure of the weight of the water in deep water being so high, that the air pressure above it is not relatively significant.

The principal theory, is that the effect of changing pressure on the swim bladders of fish makes them uncomfortable or dis-oriented. In this theory, the fish will move to feel well, or they feel bloated or full. With a lowering barometer, it is believed these fish move into deep water seeking higher water pressure and ride out the low pressure around structures. The theory suggests that just prior to change from a high to a low, fish will bite like crazy until the low hits and then stop. The difficulty with this theory, is that water is 900 times more dense than air, and generates signicantly more pressure than air. In fact,a 3 foot wave will produce a variation of pressure more significant than can be expected from a change in atmospheric pressure through a dramatic change, and the wave effect is happening every few seconds, rather than the hours or days that the atmospheric changes takes to occur.