The short version: summer yes, with care and local knowledge of your chosen spot; winter no.
The reef. A shallow limestone shelf fringes most of this coast. At low water it is exposed and sharp, and a fall on it opens skin badly. Reef shoes are not optional if you are getting in.
The channels. Where the shelf is cut, water leaving the reef moves fast and seaward. These are the sandy-looking gaps that read as the safe entry and are not.
The lifeguards. Cover along Mokulēʻia is thin and not continuous, and Army Beach has none at all. Do not plan a swim on the assumption a tower will be staffed. If nobody else is in the water on a beautiful day, there is a reason, and the reason is usually the current.
The season. From roughly November to March this is a north-facing coast taking the same North Pacific swell that closes Waimea. Waves here break over reef rather than a sand bar, which makes them less photogenic and no less dangerous. From roughly May to September the swell switches to the south side of the island and Mokulēʻia goes quiet, and that is the window when the sandy pockets are swimmable.
Portuguese man o' war get blown onto this shore on strong trade days. Blue, small, and they sting after they are dead.
If you want reliably supervised swimming on this coast, drive back to Haleʻiwa Aliʻi Beach Park or Haleʻiwa Beach Park, both of which have towers.