Canon 1118 requires that marriage take place in a Catholic Church unless there are extraordinary circumstances and then permission is needed from the Bishop of the Diocese where the wedding takes place. No liturgical function can be performed outside the parish church without permission from the local bishop. Sometimes, the bishop can issue a dispensation from this requirement if there is good pastoral reason to do so. A beach wedding does not seem to be one that presents a pastoral necessity.
In this case it would seem, then, that either there may have been extraordinary circumstances present or the priest witnessing the marriage was acting outside of the official guidelines of the Rite of Marriage.