The rarangi coastline and into port underwood is generally not the best of fishing. If you target the river mouths you have a chance of catching KY and mullets.
On the coast itself, there is the chance to catch the typical sharks and other species common to this type of beaches. But I do not rate this area highly.
Port underwood has been quite heavily fished. If you walk to a remote point you might have a chance of catching Blue cod and Gurnad. Moki and Butterfish are quite common in the outer kelp beds.
There is a decent point about a 20 minute walk south of Ocean Bay. It is a tricky walk at high tide and a bit of rock climbing should be expected.