Boats leave Redondo Pier year-round to look for whales in Santa Monica Bay. Different species are around in different seasons: grey whales migrate past from December to May, blue and humpback whales arrive to feed in June through October, and pods of common dolphins and bottlenose dolphins are present in large numbers year-round.
Two operators dominate — Voyager Excursions and Redondo Beach Whale Watch — both running trips of two to three hours several times a day in season, less frequently outside it. Trips cost around $45 per adult; sightings are routine but not guaranteed (typical operators advertise around 95% success rates in season). Bring layers — temperatures drop quickly once you are offshore — and Dramamine if you are prone to seasickness.
Booking online a day in advance is usually fine for weekday departures; weekends sell out faster.