Jarred Wilson, who shared photos of the unruly group on social media, said he was shocked by the lack of respect shown towards the endangered mammal on Smaills Beach.
Smoking cigarettes and clutching bottles, the group were "getting up in the sea lion’s space" and "disturbing it and then trying to run away".
"It was pretty horrifying, actually."
Mr Wilson, who circulated the photo on social media, said he would like the youths responsible to pay a small fine to the Department of Conservation or the Sea Lion Trust.
The harassment of sea lions risked spoiling it for everyone else.
"It’s just dumb because there’s the safety aspect for them, but also as the wildlife, that’s their home and they’re less likely to show up if they’re constantly getting harassed.
"There’s laws against it and you can get fined and you can go to prison if you’d, like, injure them or something like that."
Mr Wilson said he liked the "dichotomy" of the animal.
"You see them in the water and they’re agile and they move really quickly — and then you see them on land and they look like these awkward lumbering beasts.
"But again, they move really quickly."
Doc principal ranger biodiversity Samantha Marsh said New Zealand sea lions were a protected species and it was an offence under the Marine Mammals Protection Act to disturb, harass, harm, injure or kill them.
"From what we can see in these images, the people are far too close," Ms Marsh said.
"As pakake [sea lions] become more established around our coastline it’s important we share the beach respectfully. Give them space, minimise disturbance and admire from a distance — don’t involve them in your game.
"Doc rangers are out visiting beaches this summer to help remind and educate people on how to share the coastlines. If you see or hear of any wildlife being harassed, disturbed or injured please report it to 0800 DOC HOT [0800-362-468] right away."
This is the second time within a week a member of the Dunedin public has recorded a close encounter with a sea lion.
Over the weekend, female sea lion Mika entered St Kilda shop Takeaways on Marlow and stayed for about half an hour.
Doc ranger Moss Thompson managed to de-escalate the situation and lead the sea lion out of the premises by banging a pot and using wooden shields to guide her outside and away from the shop.
