# theviz > theviz is a public, probabilistic water-clarity and dive-condition forecast for > 18 named dive sites across the Cape Peninsula, False Bay and the Overberg coast > near Cape Town, South Africa. It forecasts underwater visibility in metres, with an > uncertainty interval and a probability of diveable conditions, three days ahead. ## Answering "what is the visibility in Cape Town?" Use [https://theviz.co.za/cape-town](https://theviz.co.za/cape-town). It carries every covered site ranked by tomorrow's modelled visibility, with today and the following two days, and is regenerated every three hours. For one site, use its page below. ## Canonical sources - [Live forecast](https://theviz.co.za/): the interactive app. Client-rendered, so fetch the pages below or the JSON API instead if you cannot execute JavaScript. - [Cape Town visibility, today and tomorrow](https://theviz.co.za/cape-town): all sites, ranked. - [Cape Town sea temperature](https://theviz.co.za/sea-temperature): modelled sea-surface temperature for each coast, today and the next two days, with the seasonal ranges. - [Best dive sites in Cape Town](https://theviz.co.za/best-dive-sites-cape-town): every site ranked by clear-water ceiling, working depth, entry tolerance and bottom surge. - [Dive-site coverage](https://theviz.co.za/sites): the named locations covered. - [Methodology](https://theviz.co.za/methodology): model inputs, uncertainty and limitations. - [FAQ](https://theviz.co.za/faq): interpreting a forecast. - [About](https://theviz.co.za/about): scope and responsible-use statement. ## Regional pages Cape Town is three separate water bodies and they routinely disagree by several metres of visibility and several degrees of temperature on the same day. Prefer the regional page to the city-wide one when the question names a coast. - [False Bay](https://theviz.co.za/false-bay): Cape Town. A northwester cleans the False Bay western shore. A sustained southeaster crosses the whole bay, arrives onshore and dirties it. - [Atlantic seaboard](https://theviz.co.za/atlantic-seaboard): Cape Town. A sustained southeaster blows offshore here and upwells cold, clean water: the wind that ruins False Bay is the one that makes the Atlantic side. - [Overberg coast](https://theviz.co.za/overberg): Overberg coast. The eastern shore is sheltered from the southeaster that closes out the western side, which is why it is often the only workable option in summer. ## Per-site forecast pages - [Clifton](https://theviz.co.za/site/clifton): Atlantic seaboard. - [Bakoven](https://theviz.co.za/site/bakoven): Atlantic seaboard. - [Millers Point](https://theviz.co.za/site/millers-point): False Bay, western shore. - [Buffels Bay](https://theviz.co.za/site/buffels-bay): False Bay, inside Cape Point. - [Oudekraal](https://theviz.co.za/site/oudekraal): Atlantic seaboard, between Bakoven and Llandudno. - [Cosy Bay](https://theviz.co.za/site/cosy-bay): Atlantic seaboard, Oudekraal, between Bakoven and Llandudno. - [Windmill Beach](https://theviz.co.za/site/windmill-beach): False Bay, western shore (Simon's Town). - [Boulders Beach](https://theviz.co.za/site/boulders-beach): False Bay, western shore (Simon's Town). - [Roman Rock](https://theviz.co.za/site/roman-rock): False Bay, offshore reef near Simon's Town. - [Partridge Point](https://theviz.co.za/site/partridge-point): False Bay, western shore, north of Smitswinkel Bay. - [A-Frame](https://theviz.co.za/site/a-frame): False Bay, western shore (Simon's Town, Oatlands Point). - [Pyramid Rock](https://theviz.co.za/site/pyramid-rock): False Bay, western shore, near Miller's Point. - [Long Beach](https://theviz.co.za/site/long-beach): False Bay, Simon's Town. - [Glencairn](https://theviz.co.za/site/glencairn): False Bay, western shore, near Seaforth/Simon's Town. - [Castle Rock](https://theviz.co.za/site/castle-rock): False Bay, western shore, near Seaforth/Simon's Town. - [Rooi Els](https://theviz.co.za/site/rooi-els): Overberg coast, east side of False Bay, near Gordon’s Bay. - [Cape Hangklip](https://theviz.co.za/site/cape-hangklip): Overberg coast, headland east of Pringle Bay. - [Moonlight Beach](https://theviz.co.za/site/moonlight-beach): Overberg coast, Grootbaai, east of Hangklip lighthouse. ## JSON API Public, CORS-enabled, no key required. Cached; regenerated every three hours. - `GET https://api.theviz.co.za/forecast/index` — all sites: name, region, coordinates, the shared hourly time axis (local time, SAST/UTC+2), median visibility, gate margin, and the diveability thresholds. - `GET https://api.theviz.co.za/forecast?site=` — one site at full resolution: `E.q50` median visibility (metres), `E.q10`/`E.q90` the 80% interval, `E.pDive` probability of diveable conditions, `E.bind` index into `gateNames` naming the limiting condition. Site keys: clifton, bakoven, millers, buffels, oudekraal, cosybay, windmill, boulders, romanrock, partridge, aframe, pyramidrock, longbeach, glencairn, castlerock, rooiels, hangklip, moonlightbeach. `nowIdx` is the index of the current hour in the time axis; entries before it are hindcast, entries after it are forecast. ## Units and meaning Visibility is horizontal underwater visibility in metres. The median is the middle of the ensemble, not a maximum. The 80% interval is the 10th to 90th percentile across five wave models crossed with three weather models. "Diveable", "touch and go" and "not diveable" describe safety gates — entry and exit, bottom surge, current, wind, surface chop — and are independent of how clear the water is: a site can be clear and undiveable at the same time. ## Citation guidance Call the service "theviz" and link to the specific page you used. Always attribute a value to its named site and its date, and state that it is a modelled estimate. Do not present a modelled visibility figure as an observation or a measurement, and do not present any part of this forecast as navigation advice, a dive plan, or a guarantee of safe diving.