As far as Welly beaches go, Island Bay is pretty awesome. The fiance and I have been spending a lot of time there recently, and neither of us can get enough.
Apart from being gorgeously rugged with a little pontoon to jump off, an island to kayak to, some crazy big seaweed, and super clear (and freezing) water, it is a beautiful place to ride our bikes through and even has a little aquarium with a 'touching pool' so you can touch weird squishy anemones and sea cucumbers (not everyones cup of tea I admit).
Basically, if you are in Welly I recommend going there!
All photos taken on Pentax M E super on Agfaphoto CT precisa film iso 100