The West Coast may just be the best coast ... because E-40 didn't have his audience waiting for hours to see him perform at SeaWorld ... unlike the Jay-Z concert at Yankee Stadium.

SeaWorld got lit Saturday when the Bay Area rapper made a huge splash at the Bayside Amphitheater in San Diego ... and the crowd was dancing, going dumb and getting hyphy.

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E-40 had a sea of people turning up ... and they weren't just in the stands. People swarmed around the banks to dance to his hits ... and tons of ladies -- and even an old head -- were twerking!

Seriously, check it out ... people were all over the place ... dancing on the stairs, the seats, and the aisles. You can feel the energy through the screen.

No word if the killer whales were bobbing their heads ... but the vibes were too good to let surface-dwellers get all the fun.