Surfing in very popular in San Diego for a good reason: there is consistently waves year round! In the summer months when the swells come from the SW waves can range from 1 foot all the way to 10 feet! In the summer waves will be big big less consistently than in the Winter, and is the best time for swimming. Some beaches may receive blockage from the channel islands and be better for swimming than others. In the Winter is when the ocean really comes to life in Southern California and the waves can get all the way up to 15-20 feet on the biggest of swells. Going in the ocean in the Winter should be reserved for water experts as the current becomes much stronger and the ocean becomes more dangerous.