There are two separate jobs here and most app roundups blur them. One is knowing where the rocks are. The other is knowing what the wind will do. Very few apps are good at both, and the ones that claim to be are usually strong at one and adequate at the other.
For a charter week you want one from each column. Here is what we actually put on a phone before a trip.
Charts and Navigation
Navionics — The Default, and Rightly So
Garmin-owned, and the most widely used marine charting app in the world. If the boat has a plotter, there is a decent chance it is running Navionics data already, which means your phone and the plotter agree with each other. That is worth more than it sounds at two in the morning.
The chart quality in European waters is the reference standard. Depth contours, harbour plans, navigation marks, restricted areas. The Sonar Chart layer, built from crowdsourced depth logs, is often more detailed inshore than the official survey, which is useful in the kind of shallow Croatian bay where the official chart says "unsurveyed".
You can overlay wind, pressure and tide on the chart and see how the forecast lines up with the route you have drawn. That is a genuinely good feature and it is not a substitute for a real weather app — it shows one model, with no sense of how much the models disagree.
Cost: roughly £25 a year for a regional chart subscription. Buy the region, not the world.
savvy navvy — Better If You Want to Be Told What to Do
savvy navvy took the Navionics problem — here are the charts, you work it out — and inverted it. You enter where you are and where you want to go, and it produces a route with waypoints, accounting for depth, tides and the wind forecast, and tells you when to leave.
For charter sailors this is a good trade. Most people chartering a 45-footer in Greece for a week are competent but out of practice, and having the passage plan drafted for you to check is more useful than a blank chart. The tidal work in particular, in places like the Channel Islands or the Solent, is well done.
The limitation is the flip side of the strength. It gives you an answer rather than the information to form one, and its routing is conservative in ways that occasionally make no sense locally — it does not know that everyone takes the inside passage because the current runs the right way at that state of tide.
Use it as a first draft and check it against the chart.
The Boat's Plotter
Worth saying plainly because it gets lost in app comparisons: the plotter mounted in the cockpit is the primary navigation instrument, and your phone is the backup. Phones overheat in an August cockpit, die at inconvenient moments, and are unreadable in direct sun with polarised sunglasses on.
Check on handover day that the plotter's charts are current and that you know how to work it. Ask the base to show you, even if you think you know the brand. Five minutes on the dock is cheaper than half an hour offshore.
Weather
Windy — Install This One
Windy's advantage is that it shows several forecast models — ECMWF, GFS, ICON and others — over the same map, and you can flip between them.
That matters more than any single forecast. If ECMWF and GFS both say 18 knots from the northwest on Thursday, that is a forecast you can plan around. If one says 12 from the north and the other says 25 from the west, the honest read is that nobody knows yet, and you should keep Thursday flexible. No single-model app will ever tell you this, because a single model always sounds certain.
For the Aegean specifically, Windy is how you watch a meltemi build. That wind runs 25 to 35 knots for days at a time from mid-July to mid-August, and the difference between a good Cyclades week and a miserable one is often just seeing it three days out and rearranging the route. More on the seasonal picture in Best Greek Islands for a Sailing Holiday.
Cost: free tier is genuinely sufficient for charter use.
PredictWind — Serious, Expensive, and Probably Not for You
PredictWind runs up to eleven forecast models and does proper weather routing — you give it the boat's polars and it calculates the fastest or safest route, with a departure planner that tells you which day to leave.
It is the standard for offshore passage-making and ocean crossings. For a week hopping between Croatian islands it is considerable overkill, and the pricing reflects the audience: basic forecasts start around €29 a year, but the routing tiers that justify the app run from roughly €274 a year to about €499 for the professional version.
If you are crossing a Biscay or planning an Atlantic passage, it is worth every penny. For a charter, it is not the tool.
The Local Forecast
Every Mediterranean charter country runs a national marine forecast, and the local product frequently beats the global models in coastal waters because it is tuned for local effects. Croatia's DHMZ, Greece's HNMS, Italy's Meteomar. The base manager will tell you which one they trust and will usually have it pinned somewhere in the office.
Ask on handover day. It takes thirty seconds and the answer is better than anything you will find by searching.
What We Put on a Phone Before a Charter
Four things, and only one of them costs anything meaningful.
Navionics with the regional chart pack downloaded for offline use, because data coverage in the islands is unreliable and a chart that needs a signal is not a chart.
Windy, free tier, with the model comparison bookmarked for the cruising area.
Navily for anchorages and berths — covered properly in The Best Apps for Finding a Marina and Booking a Berth, and the anchorage reviews are the single most useful crowdsourced dataset in Mediterranean sailing.
Whatever the base recommends for local weather.
That is it. savvy navvy goes on the list too if you want passage plans drafted rather than drawn, and it is a reasonable £20-odd a month for the season.
The Part Apps Do Not Solve
An app will tell you it is going to blow 30 knots on Thursday. It will not tell you whether your crew can handle 30 knots, whether the anchorage you were heading for has any shelter from that direction, or whether the sensible move is to sit tight for a day and lose a stop from the itinerary.
That judgement is the actual skill, and it is why a skippered charter is a reasonable choice for a lot of groups even when someone technically holds the licence. We wrote about where that line sits in Bareboat vs Crewed Charter, and about the licence rules themselves in Can You Charter a Yacht Without a Licence.
Build flexibility into the route rather than confidence into the plan. A week with two spare afternoons in it survives a bad forecast. A week with a restaurant booking every evening does not.