Every principal building shall be built upon a lot with frontage upon a public street improved to meet the municipal requirements or for which such improvement has been guaranteed by the posting of a performance guarantee pursuant to this chapter unless relief has been granted under the provisions of N.J.S.A. 40:55D-36. In the case of a lot fronting on the Navesink River, the frontage on the river may be considered as lot frontage for the purpose of determining compliance with the frontage requirement of the zone provided that the lot has a right-of-way, that is owned fee-simple absolute as part of the lot, with a minimum width of 20 feet that fronts on, provides access to, and connects the lot with an improved public street.