The close encounter was caught on video from aboard Newport Coastal Adventure.
Mark Girardeau said the calf appeared to be just days old as it still had fetal folds.
The curious calf was spotted checking out the boat with its mother close behind.
After getting a closer glimpse, the mother guided the calf back on course.
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Gray whales migrate south from Alaska to Mexico during the winter months, passing right along the coast of Southern California.
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