I suspect most were hunters, at least at first.
Then the hunters started spearing fish in shallow rivers and streams, as well as coastal waters, most likely.
Probably hunters and gatherers near the shorelines.
I recall hearing stories from less than 100 years ago, of people wading into the shallows to pull truckloads of abalone from off the rocks at low tide.
Similarly, 200 – 300 years ago, people were doing the same with Maine lobsters on the East Coast. Apparently, they were so plentiful that they were almost wading on shore, taking over the beaches (note – a small exaggeratin on my part). Some of the early local workers had it put into their contracts that they would only stand being served so much lobster by their employers during a week/month, since it was growing tiresome to them.
Today, it's a rare, and expensive delicacy, like the abalone.