Comparison

Navigation Rules Pro vs Shellback

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

Head to head
About

Navigation Rules Pro

This app provides comprehensive boating regulations and reference materials, including international and inland navigation rules, sound and light signals, and communication information. It features quick references, calculators, and unit conversions for boaters.

Highlights
  • International and Inland Navigation Rules
  • Sound and Light Signals Quick Reference
  • Aids to Navigation (AtoN)
  • Communication Information (DSC, Morse Code, etc.)
  • Boating Calculators
  • Unit Conversions
  • Search and Favorites functionality
Features
Currently charting
Read full description

Navigation Rules Pro has everything in our popular Navigation Rules app plus over 100 pages of additional important reference material. Navigation Rules Pro contains a complete copy of the International Regulations for Preventing Collisions at Sea, 1972 (COLREGS), including amendments and the Inland Navigation Rules, in effect for all inland waters, including the Great Lakes plus the following information a boater needs: * Sound and Light Signals Quick Reference * Steering and Sailing Rules Quick Reference * Aids to Navigation (AtoN) * Bridge Lighting Quick Reference * Lock Procedures * U.S. Federal Requirements for Recreational Boats * Communication information - DSC, Rescue 21, International Code Signals, semaphore flags, distress signals, phonetic alphabet, prowords, international morse code. * Weather and Oceanography * Law Enforcement * Boating Calculators * Unit Conversions Navigation Rules Pro includes the COLREGs most recent version dated - June 28th, 2019. This app includes an annotated table of contents and a search function to help the reader quickly find the rule and related references. A Favorites page allows quick access to commonly referenced pages. Use the email function to share a page with others. If you are a boater you need to know this information.

About

Shellback

This app provides US Naval Surface Force personnel with offline access to essential information. It includes manuals and resources for administration, medical, operations, personnel management, safety, and navigation rules. Content is updated annually for relevance.

Highlights
  • Offline access to SURFOR information
  • Admin/Training manuals
  • Medical readiness resources
  • Operations and navigation training
  • Personnel management documents
  • Safety information and lessons learned
  • Rules of the Road quiz
Features
Read full description

What is the Shellback app? Shellback, formerly known as eDivo, is a free mobile app developed to support US Naval Surface Force (SURFOR) personnel in an easy-to-access offline environment. What is a Shellback? In naval tradition, a Shellback is a nickname for a Sailor who has crossed the Equator and thus transitioned from a novice Sailor, or Pollywog, to an experienced Sailor. Why do I need Shellback? Shellback provides Sailors the ability to download key SURFOR information on their own portable devices and access it while underway without the need for an internet connection. Shellback provides the most relevant and current information to SURFOR Sailors in one location. Content is scheduled for annual updates. What type of info can I find in Shellback? The information in Shellback is separated into several main categories: -Admin/Training: Contains the Correspondence Manual and the SURFOR Training and Readiness Manual. -Medical: Includes the Manual of the Medical Department, information on medical and physical readiness, mental health, Medical Evaluation Board procedures, the Disability Evaluation System, family member readiness, and more. -Operations: Includes information and training on bridge management, navigation basics, watch team tools, crew endurance, operating procedures for air-capable ships, Air Certification for Naval Surface Force Ships, and manuals for amphibs, maintenance, and other general ship operation resources. -Personnel Management: Provides documents on Navy personnel policy and administration. Also includes legal handbooks and manuals, resources for Surface Warfare Officers, and a variety of general personnel management resources. -Safety: Provides documents related to lessons learned, mishap reporting, notices, safety-related awards, and general safety resources. -Rules of the Road: This quiz tests a Sailor’s knowledge of maritime navigation rules.

Screenshots

Navigation Rules Pro4 screens
Shellback3 screens

Verdict

The call

The clearest difference is price: Shellback at Free against Navigation Rules Pro's $4.99. Navigation Rules Pro's advantage is rating (4.8 vs 3.2) and review sentiment (85% vs 45%). On ads, in-app purchases and device support there is nothing between them.

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

Shellback is free to download; Navigation Rules Pro costs $4.99 up front. Neither carries in-app purchases, so what you see is what you pay.

ReceptionRating · Positive reviews · Number of ratings

Navigation Rules Pro holds the better App Store score, 4.8 against 3.2. That said, the two scores are not equally well evidenced: Navigation Rules Pro has 442 ratings behind it against 38, so its average is the more settled of the two. Written reviews point the same way: 85% of Navigation Rules Pro's written reviews are positive against 45% of Shellback's.

UpkeepUpdate frequency

Navigation Rules Pro ships an update every 3 months, Shellback every 10 months. The most recent releases landed on September 24, 2026 and June 9, 2026 respectively.

Scorecard8 real differences · 3 level
Navigation Rules Pro versus Shellback: the parameters behind the verdict, then further details
ParameterNavigation Rules ProShellback
Price$4.99Free — better
Rating4.8 (442 ratings) — better3.2 (38 ratings)
Positive reviews85.0% of reviews — better45.2% of reviews
Number of ratings442 — better38
Update frequencyEvery 3 months — betterEvery 10 months
AdsNoNo
In-app purchasesNoNo
MonetizationPaidFree — better
Best chart rank#37 — better—
DevicesiPhone, iPad, iPodiPhone, iPad, iPod
Requires iOS9.3 — better15.0
Further details — not scored
Size37 MB71 MB
Age rating4+12+
DeveloperCalculated IndustriesProgram Executive Office for Enterprise Information Systems, Sea Warrior Program

Customer experience

Navigation Rules Pro

All ratings442 ratings
Positive96.6%
Neutral1.4%
Negative2.0%
Written reviews40 reviews
Positive85.0%
Neutral7.5%
Negative7.5%

Shellback

All ratings38 ratings
Positive52.6%
Neutral5.3%
Negative42.1%
Written reviews42 reviews
Positive45.2%
Neutral19.0%
Negative35.7%

In-app purchases

None

Navigation Rules Pro

No in-app purchases

None

Shellback

No in-app purchases

Questions

Is Navigation Rules Pro free?
Navigation Rules Pro costs $4.99, with no in-app purchases.
Is Shellback free?
Shellback is free to download, with no in-app purchases.
Which has better reviews, Navigation Rules Pro or Shellback?
Navigation Rules Pro is rated higher. Navigation Rules Pro averages 4.8 out of 5 from 442 ratings, while Shellback averages 3.2 from 38 ratings.
Do Navigation Rules Pro or Shellback have ads?
Neither Navigation Rules Pro nor Shellback shows ads.
Which is updated more often, Navigation Rules Pro or Shellback?
Navigation Rules Pro ships an update every 3 months, and Shellback every 10 months. Most recently, Navigation Rules Pro was updated on September 24, 2026 and Shellback on June 9, 2026.

Other comparisons