Seaidx FAQ
Common questions about Seaidx — what it is, how tide predictions and the Ocean Viewing Index work, and where the data comes from.
What is Seaidx?
Seaidx is a free coastal sightseeing planner at seaidx.com. It covers 183 destinations across Asia-Pacific and Europe. Every destination gets a daily Ocean Viewing Index (OVI) — a 0–100 score for how rewarding the view is likely to be — and every ocean-facing destination also shows 7-day tide predictions, satellite-based sea color, and the weather factors that shape the view. It is free, ad-free, requires no account, and is built by VoyBird, the independent team behind FujiVis (Mount Fuji visibility) and JP HANABI (Japan fireworks calendar).
How is Seaidx different from a tide chart website?
A tide chart answers one question: when is the water high or low. Seaidx answers the follow-up question travelers actually ask — will the sea look good today? On top of tide times it computes the Ocean Viewing Index, which weighs water color, clarity, atmospheric visibility, sea state, daylight, and algal-bloom risk into a single 0–100 score. Use the tide chart to pick the hour; use OVI to pick the day. Seaidx gives you both on the same destination page.
How accurate are Seaidx tide predictions?
Tides are computed from the FES2022b global ocean tide atlas (AVISO/CNES), using 34 harmonic constituents extracted for each destination — the same class of model used by professional oceanographic services. FES2022b typically reproduces tides to within a few centimeters in the open ocean; errors grow in narrow bays, river mouths, and harbors, so always treat local official notices as authoritative for navigation or safety.
What is a good Ocean Viewing Index score?
OVI runs from 0 to 100 in five bands: 80 or above is Excellent (highly recommended), 65–79 Good (worth a visit), 50–64 Fair (sea color may look muted), 35–49 Poor, and below 35 Bad. Heavy sea fog can subtract up to 50 points and algal-bloom risk up to 30, because both routinely ruin an otherwise promising view.
Where does Seaidx data come from?
Tides: the FES2022b global tide model with UHSLC tide-gauge observations for validation. Sea color: satellite ocean-color products from the Copernicus Marine Service, with a global monthly climatology (Pitarch et al., 2021) as a clearly-labeled fallback when recent satellite data is unavailable. Weather and waves: Open-Meteo forecast models. Basemap: OpenStreetMap. Every location page lists which source fed each number.
How often is Seaidx updated?
Tide predictions and the Ocean Viewing Index are recomputed daily for every destination, and the 7-day outlook refreshes with each day's forecast data. Satellite sea color arrives with its observation lag; when a destination's freshest satellite pass is not yet available, Seaidx shows the monthly climatology value marked with an 'estimated' badge instead of pretending to have an observation.
Which destinations does Seaidx cover?
183 coastal destinations across Asia-Pacific and Europe — from Enoshima and Okinawa in Japan, to Phuket, Bali, and Da Nang in Southeast Asia, Sydney's Bondi Beach and the Gold Coast in Australia, Auckland and Piha in New Zealand, to Nice on the French Riviera, the Algarve, and the Norwegian coast around Bergen. Browse the full list at seaidx.com/locations, searchable by name, country, or 'near me'.
Can I use Seaidx for surfing or swimming safety?
No. Seaidx is designed for sightseeing and trip planning, not for surf break selection, swim safety, or navigation. Its sea-state input describes how the surface looks, not whether it is safe to enter. For surfing, swimming, or boating decisions, use official marine forecasts, lifeguard advice, and local warnings.
Why does sea color sometimes show an 'estimated' badge?
Satellite ocean color needs a clear recent pass over that patch of ocean. When clouds block the latest passes or the newest data has not been published yet, Seaidx falls back to that location's monthly climatology — a real long-term average, not a guess — and labels it with a badge so you know exactly what you are looking at. Seaidx never shows invented numbers.
Is Seaidx free? Is there an app?
Seaidx is completely free, has no ads, and needs no sign-up. It works in any mobile or desktop browser at seaidx.com — there is no separate app to install. It is one of three free travel tools from VoyBird; the others are FujiVis for Mount Fuji visibility and JP HANABI for Japan fireworks festival schedules.
Still planning a coastal trip?
Read the Ocean Viewing Index vs tide forecast guide, browse all 183 destinations, or learn more on the about & methodology page.