Multipath routing protocols trade off the effort of replicating data packets through multiple routes for improved delivery ratio or end-to-end delay. These advantages are especially valuable for those underwater networking applications where reliable data delivery justifies a higher resource consumption. In this letter, we argue that choosing multipath routes according only to the node- and link-disjoint paradigms may lead to excessive interference in underwater networks, even in the presence of MAC protocols based on interference avoidance. We show that it is more convenient to directly choose multipath routes that cause little interference to one another, and propose a multipath routing protocol that distributedly implements this concept. We simulate our solution in underwater network scenarios, and show that it achieves better packet delivery ratio and fewer interference-induced packet losses with respect to standard multipath routing approaches, even when the latter are stacked on top of interference-avoiding MAC protocols.