There is a hybrid category among bodies of water, something between a swimming pool and a natural beach. Recognition of that could mean more appropriate regulation of public health for people who would like to take a dip in these kinds of “pools.”

This could include recreational assets such as the Wai Kai Lagoon in Ewa Beach and, at least in theory, the Waikiki War Memorial Natatorium, where regulatory concerns as well as the high cost of renovation have kept that saltwater pool shut down for years.

But for the more immediate future, lawmakers could enable swimming to resume at Wai Kai, if legislation passes, as it should. The lagoon is a manmade water feature at Hoakalei Resort, excavated by the developer but naturally filled, through porous rock, by fresh groundwater mixing with saltwater from the adjacent shoreline.

Hoakalei was originally conceived with the name Ewa Marina. But a decade ago developer Haseko Hawaii decided instead it would be realized as a lagoon, surrounded by residences and with retail and hotel projects planned in future phases.

Until 2018, there had been some swimming in the lagoon as well as other recreational activities. That’s when a complaint to the state Department of Health (DOH) compelled Haseko to close it to swimming. There had been no water-quality problem, but officials recognized that under current legal definitions the lagoon would qualify as a swimming pool.

This would require a full exchange of water every six hours, among other standards enforced for pools, which would be impossible for something like a lagoon. That’s when the “no swimming” signs went up.

So Senate Bill 2804 and its companion House Bill 1743 were introduced, seeking to redefine “pools” subject to health rules as “watertight artificial structures containing a body of water that does not exchange water with any other body of water, either naturally or mechanically, and is used for swimming, diving, recreational bathing, or therapy by humans.”

Under this language, Wai Kai, the Natatorium and other recreational bodies that are not “watertight” could come under state water-quality oversight for public health, but would no longer be subject to the stricter standards of a conventional swimming pool.

Where the Natatorium is concerned, there are other factors at play, not the least of which is finding the estimated $31.8 million cost for restoring that pool to working order. But fixing a reasonable standard is a rational starting point.

“The DOH already has public health standards for other public recreational waters such as our beaches, which should be applied if the owner intends to use the lagoon or ocean venue for swimming,” Peter Oshiro said in written testimony. Oshiro heads the Food Safety Branch, which also handles regulation of swimming pools.

This would make sense, especially given that ongoing testing by Haseko has found the water to be cleaner than some beaches — partly because of the seepage of groundwater, in and out.

Another consideration at issue here is public access. The developers have enabled some public access to the lagoon from the shoreline currently — and have committed to expanding that when the hotel and retail projects are built out.

That is good. As designed, the lagoon functions as an extension of the shoreline, tapping into both the fresh- and seawater that are public resources. Haseko is right to acknowledge that public access is warranted, and must be held to that pledge.

In the meantime, the proposed change in a simple legal definition of “pool” will remove one barrier to full use of a recreational asset the public should be able to enjoy.