In one illustrative embodiment, there is provided a boot sole system for guiding a fin, the system comprising: at least one toe sole body connectable to the fin and comprising first and second stop surfaces; a posterior sole body comprising third and fourth stop surfaces; and a transverse hinge for hingedly connecting the at least one toe sole body to the posterior sole body to permit longitudinal deflection of the at least one toe sole body relative to the posterior sole body in a first deflection direction and in a second deflection direction opposite the first deflection direction. The first, second, third, and fourth stop surfaces are positioned to restrict longitudinal deflection of the at least one toe sole body relative to the posterior sole body in the first deflection direction and in the second deflection direction. Fins are also disclosed.