A bridge, like a boat, is a construct. In war, bridges are usually destroyed, for tactical reasons. In peace, bridges allow for travel and supply of goods.
Mostly, thanks to bridges, we don't have to swim, fjord, drown, be delayed, get ourselves and stuff wet.
Consciousness, spirit world - the Water is a metaphor (as with our sexuality). E.g. "Swimming in [specific emotion]." Drowning in debt. Floating on cloud 9. Carried away by [vice]. Murky, shallow, clear, deep ...
A bridge is rational.