His little boat has no cabin and carries three people at most. They always wear lifejackets.
He watches the weather and swells carefully. He has been caught out by high wind once, knows how fast that can happen and only goes out when it is flat calm.
"If it's dodgy, we just don't go - we don't chance it. You always know that eventually there's going to be a good day."
Mornings tend to be calmer and he said February, March and April were the best months for fishing. Catches are especially good north of Kai Iwi, where there are blue cod and snapper grounds.
Ironsand mining could disrupt that, he said, if Trans-Tasman Resources gets consent to mine 66sq km of seabed.
"Boats do fish that area."
Most of the mishaps at sea are caused by engine trouble, so Mr Johnson gets his boat's engines checked every year. He once had a propeller problem, could only idle his motor and limped home slowly.
Staying in radio contact with Coastguard Wanganui is another major safety measure.
There is one radio in the boat and Mr Johnson has a waterproof VHF radio attached to his lifejacket, in case he goes overboard and needs help.
He has never met the four coastguard radio operators but whenever he goes out he tells them where he launched, how many people are in the boat, roughly where he is going and when he plans to return.
If he knows he is running late he will radio and let them know, because if he is more than half an hour overdue they begin a rescue operation.
He will also radio in when he is back at the beach or slipway.
"They're always polite and easy to deal with," he said.
He has fished on the East Cape and said neither the fishing nor the coastguard service there was as good as Wanganui's.
