Comparison

Sea Depth vs Depthly

Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.

Head to head
About

Sea Depth

Visualize detailed underwater terrain with high-resolution bathymetric charts. Gain deeper insights into seafloor structure, contours, and terrain for offshore activities. Includes optional data overlays and waypoint management for enhanced situational awareness.

Highlights
  • High-resolution shaded-relief bathymetry
  • Detailed depth contours with intelligent labeling
  • Optional data overlays (pipelines, bottom composition)
  • GPX waypoint import/export
  • Drift Test tool
  • Offline chart access
Features
Read full description

SeaDepth delivers professional-grade bathymetric charts for anglers looking to add a new level of detail and insight offshore. Built using high-resolution survey data and advanced shaded-relief techniques, SeaDepth reveals underwater structure, contours, and terrain that traditional charts often fail to show. The result is a clearer, more intuitive view of the seafloor - helping anglers and captains better understand offshore environments before and during time on the water. In addition to detailed depth visualization, SeaDepth offers optional data overlays, intelligent contour labeling, waypoint interoperability, and analytical tools that enhance situational awareness offshore. Key Features • High-resolution shaded-relief bathymetry • Detailed, clearly labeled depth contours • Intelligent contour interval scaling by depth range • Pipeline overlay (Gulf of America) • Bottom composition overlays highlighting seafloor characteristics • GPX waypoint import and export for interoperability with other platforms • Drift Test tool to observe drift direction and speed over time • Offline chart access for use beyond cellular coverage • Smooth zooming and panning optimized for offshore use Depth Contours with Intelligent Labeling SeaDepth uses a graduated contour labeling scheme designed to provide maximum detail where it matters most, while maintaining clarity and performance in deeper  depths: • 1-foot contour intervals from 1 to 500 feet • 10-foot contour intervals from 500 to 2,500 feet • 80-foot contour intervals from 2,500 feet to abyssal depths This approach delivers high-resolution insight in shallow and mid-depth areas while avoiding visual clutter in deepwater environments. Overlay Intelligence SeaDepth allows users to enable optional overlay layers such as pipelines and bottom composition data in supported regions, including the Gulf of America. These overlays provide additional context and help users interpret bottom features and structural edges with greater confidence. All available overlay layers are included at no additional charge. Waypoint Management (GPX Support) SeaDepth supports importing and exporting waypoints using the GPX file format, making it easy to move data between SeaDepth and other compatible marine devices, charting software, or planning tools. This allows users to maintain consistent waypoint libraries across platforms. SeaDrift-Drift Test Feature The built-in Drift Test feature helps users evaluate drift behavior by tracking movement over time. This is especially useful when assessing current and wind influence to have more productive drifts. Built for Offshore Reliability Charts, overlays, and waypoint data are stored locally on the device, allowing SeaDepth to function reliably offshore where connectivity may be limited or unavailable. Performance and usability are optimized for real-world offshore conditions. Disclaimer SeaDepth is intended as a supplemental planning and visualization tool only. It is not a substitute for official nautical charts, onboard navigation systems, or prudent seamanship. Terms of Use: https://www.apple.com/legal/internet-services/itunes/dev/stdeula/

About

Depthly

Features
Read full description

Know how deep the water is before you get there. Depthly turns your iPhone into a pocket depth chart for the sea. Aim the crosshair anywhere on the map, tap once, and read the depth of the seabed at that exact spot. No sonar hardware, no cables, and nothing to install on your boat. BUILT FOR PEOPLE ON THE WATER Whether you sail, fish, cruise, paddle or dive, the question is always the same: how deep is it here? Depthly answers it in one tap, using published bathymetric survey data that covers seas around the world, with especially detailed coverage of European waters. TAP TO SOUND Take a sounding anywhere on the chart. Every measurement is saved as a pin with the depth, the exact position in decimal or degrees and minutes, the nearest place name and the time it was taken. Build your own private chart of the places that matter to you: anchorages, fishing marks, shallow passages, dive sites. DEPTH CONTOURS ON ANY MAP Generate depth contour lines for the area on your screen, at the interval you choose, drawn over a marine chart, a satellite view or a standard map. See at a glance where the bottom shelves, where the deep channel runs and where it gets thin. SEABED PROFILES Pick two points and Depthly draws the cross section of the seabed between them, with the total distance, the deepest and shallowest points and the average depth. Perfect for checking a passage, planning a dive or understanding a fishing ground. WORKS COMPLETELY OFFLINE Download the chart and the depth data for a whole cruising area before you leave the marina. Out on the water, with no signal at all, soundings, contours and profiles keep working exactly as they do at home. Your charts do not need the internet once they are on your phone. RECORD YOUR TRACKS Record your route while you are underway. Depthly logs your position and fills in the depth beneath you along the whole track, even if you were offline at the time. Review the track later on the map, see the seabed profile under your route, and keep a log of every trip. TAKE YOUR DATA WITH YOU Export tracks and seabed profiles as GPX or CSV files that open in chartplotters, mapping tools and spreadsheets. Depths are written the way chartplotters expect, so your recorded data slots straight into the rest of your navigation setup. TRUSTED SOURCES Depth data comes from EMODnet Bathymetry and GEBCO, the leading public bathymetric surveys. Depthly is a planning and reference tool: always use official charts and your own judgement for navigation. FREE TO USE, PRO IF YOU WANT MORE The free version includes five depth soundings every day, all map styles and unlimited track recording. Depthly Pro unlocks unlimited soundings, depth contours, seabed profiles, offline areas, GPX and CSV export and iCloud track sync. Pro is available as a monthly or annual subscription, or as a single lifetime purchase. The annual plan starts with a seven day free trial. Subscriptions renew automatically unless cancelled at least 24 hours before the end of the current period, and can be managed or cancelled in your App Store account settings at any time. Terms of Use: https://www.apple.com/legal/internet-services/itunes/dev/stdeula/ Privacy Policy: https://blayasoft.com/privacy.html Drop a pin on the sea and know what is under it. Download Depthly and take your first sounding today.

Screenshots

Sea Depth4 screens
Depthly4 screens

Verdict

The call

Sea Depth and Depthly are too close to call on the numbers: across 5 compared parameters — price, ads, in-app purchases and device support among them — neither pulls far enough ahead to decide it. What separates them is feature set and interface, not measurable difference.

Scored on Price · Rating · Positive reviews · Number of ratings · Update frequency · Ads · In-app purchases · Monetization · Best chart rank · Devices · Requires iOS

CostPrice · In-app purchases · Ads · Monetization

Both are free to download. Sea Depth sells 10 in-app purchases, starting at $99.99 per year and Depthly sells 3 in-app purchases, starting at $3.99 per month. Whichever you choose, the download price is not the number that matters.

ScorecardNo meaningful differences
Sea Depth versus Depthly: the parameters behind the verdict, then further details
ParameterSea DepthDepthly
PriceFreeFree
Rating4.4 (14 ratings) — better—
Positive reviews100.0% of reviews—
Number of ratings14 — better—
Update frequencyEvery 5 days—
AdsNoNo
In-app purchasesYesYes
MonetizationFree with in-app purchases—
DevicesiPhone, iPad, iPod — betteriPhone, iPad
Requires iOS15.0 — better16.0
Further details — not scored
Size106 MB23 MB
Age rating4+4+
DeveloperSeadepth Charts, LLCIvan Blajic

In-app purchases

10 purchases

Sea Depth

Subscriptions1
  • Premium Charts Access7 Days trial$99.991 Year
One-time9
  • Western GOA 50%$150.00
  • Eastern GOA 30%$209.99
  • Cental GOA 20%$239.99
Show 6 more
  • Eastern GOA 20%$239.99
  • Cental GOA$300.00
  • Western GOA$300.00
  • Eastern GOA$300.00
  • Florida-West Coast$300.00
  • South Florida/Northern Bahamas$300.00
3 purchases

Depthly

Subscriptions2
  • Monthly Premium$3.991 Month
  • Annual Premium7 Days trial$19.991 Year
One-time1
  • Lifetime Premium$49.99

Questions

Is Sea Depth free?
Sea Depth is free to download, with in-app purchases available.
Is Depthly free?
Depthly is free to download, with in-app purchases available.
Do Sea Depth or Depthly have ads?
Neither Sea Depth nor Depthly shows ads.

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