At a public Carlsbad beach on Agua Hedionda Lagoon. The name translates to stinky waters, which is a consequence of the mud flats to the east that are uncovered at low tide. Low tide is not a good time for water contact for people or dogs because there is a black mud just past the water line.
This is a local favorite launch for kayak or SUP. Carlsbad requires registration with the city for passive watercraft.