However, De Vos recommends coming equipped with a wetsuit, or to be prepared to hire one: "It's been slightly colder, so people without wetsuits don't stay in the water as long.
"Generally you need to be able to remain still if you want to observe fish. And of course people without wetsuits get out sooner, having used up more energy swimming around."
The reserve has an abundance of Australasian snapper, some of which come in close to divers, perhaps remembering an era about 10 years ago when visitors were encouraged to feed fish. The Department of Conservation no longer allows this.
After the road to Goat Island was re-shaped in 1998, mud run-off caused crayfish numbers to fall by 85 per cent, said former Seafriends owner Floor Anthoni.
Seafriends last year hosted several school groups which made torch-lit night dives in the marine reserve.
Snorkellers intending to swim out to rocky Goat Island should carry footwear (jandals or sandals), to protect their feet.