This paper reviews the feasibility in function and design of an alternative to the jetty-hardened coastal inlet to develop tidal exchange between the ocean and an estuary. The proposed alternative is a subseabed (buried) tidal siphon. The proposed siphon will be best suited for inlets where navigation is not required and a tidal lag can be tolerated. The four main objectives of this paper are: (1) to present the immediate reasons for coastal inlet closures; (2) to identify the tidal exchange best suited for the tidal siphon; (3) to determine the shallowest functional depth of the inlet/outfall; and (4) to evaluate the hydraulic performance of the designed tidal siphon. It was determined the best tidal exchange for the tidal siphon is in the lower one-third of the stable tidal prism, the stability prism, and the reasonable depth for the offshore inlet/outfall structure is the depth of closure. Based on an analytical evaluation, the tidal siphon as designed preformed as required. Collection of field data included offshore wave height and length, turbidity as a function of elevation from the oceanbed, tidal range in the lagoon and tidal lag as a function of offshore tide, and inlet velocity as a function of tidal phase. The estuary used in this study is a recently constructed tidal inlet at the Batiquitos Lagoon in Carlsbad, Calif.