Pretty sure this happened in England. Maybe the seal saw a Great White Snaggle-Toothed Homosexual Shark and swam for its life.
Wtf, that's sick! I had one try to get on my shortboard during a good size winter swell. A set was coming through, and I just knew he was going to end up super close to me. He popped up and tried getting on my board in one motion. I was startled and gently swatted at him, and he swatted back, so we high fived. Seriously. He backed off a few feet and looked at me like "wtf bro?".
That happened to me too! Oceanside CA. A sealion dived under me and twisted hitting my feet with both flippers, then surfaced like he was coming on board and he was barking. I clearly remember the thought of " Am I going to have to punch a sealion in the face?" but then he just backed off and kept going. He didn't bother anyone else. just me. I was freaked out. Someone told me they are acting weird because they were sick from pollution but who knows.