Some peak coastal water temperatures across SoCal yesterday:
Santa Monica: 77°F
Long Beach: 73°F
Capistrano Beach: 74°F
Oceanside: 76°F
Encinitas: 76°F
Del Mar: 76°F
La Jolla: 76°F
San Diego Bay: 77°F
Locally, waters could approach 80°F in August/September.