Concerns have been raised about the welfare of the seal on Selsey beach.
Reports have come in about members of the public throwing stones at the mammal and letting their dogs get too close.
Jack Olley, 23, who lives in Sunnymead Drive, has just finished his degree in wildlife conservation and is now doing a masters degree in sustainability.
He said: "People are throwing stones at it. I saw a grown man going really close and disturbing it. You can take pictures from a safe place but this guy was getting too close. [The seal] sits on the beach and moves up when the water moves up, it's a big part of its life cycle.
Jack described himself as 'not much of a seal expert' so he decided to contact Seal Protection Action Group (SPAG) for guidance.
Director of SPAG Andy Ottaway said: "We are more than aware that wild animals like seal are suffering increasing disturbance and harassment. I don't think people realise just how often it's happening.
"If it is constantly disturbed and having to rush into the sea it can do the animal quite considerable harm and people don't realise the harm they are causing — it's important to maintain a respectful distance, they don't know your intentions."
Andy recommends a minimum distance of 100 yards.
Seals will use beaches to rest, pup, or spend time if they are injured. The seal on Selsey beach is being monitored and other organisations may intervene if it appears to be injured.
Andy called the news of people allegedly throwing stones at the seal 'shocking and criminal': "These things should be reported to the police and caught on camera. The hardest thing is trying to identify the people who do it.
"It's just mindless why they would like to injure or harass an animal like that."
Seals dying due to being harassment has been documented, Andy says, and they can injured themselves trying to flee situations.