Fish B.I.L.L.

B.I.L.L. Breaks. Isotherms. Layers. Location.

The satellite chart that carries the break forward to the hour you arrive.

View plans Free Report

At launch: free SST and tap-to-read; Pro is $34.99/month or $99.99/year. Final App Store prices may vary.

Project the break

A satellite pass is a snapshot. Current and wind can move the edge before you arrive.

How far the edge walks while the chart holds still
Edge, as last seen Edge, carried forward 10 NM 5 0 10.4 NM 05:00 11:00 21:00 07:00 PASS POSTED FUEL BOUGHT YOU ARRIVE

What cloud cover changes.

Cloud can block infrared temperature readings. Altimetry may still show eddy context; projections need current and wind data.

Two wavelengths, one cloud
INFRARED RADAR

{{ readHeading }}

{{ readSub }}

{{ readTitle }} {{ readStamp }}
Clear pass, temperature observed Partial observation coverage Clouded out

Eddy science

How sea-height data reveals eddies.

Radar altimetry measures sea height; broad anomalies can reveal and track mesoscale eddies.

A radar-altimetry example from the research record
RADAR ALTIMETER 1,336 KM ORBIT RANGE TO FLAT WATER SHORTER RANGE OVER THE DOME 8 cm 90 KM TYPICAL RADIUS SLOPE DRIVES THE FLOW

Cross-section through an anticyclonic (warm-core) eddy. Vertical scale exaggerated roughly 200,000× — stated, not hidden.

8 cm
Mean amplitude of a long-lived eddy, from 35,891 tracked in sixteen years of altimetry
3.5 cm
Published two-day Sentinel-6 sea-height accuracy used here as a science reference
32 wk
Average lifetime, travelling about 550 km before it loses its identity

Six planning inputs, one chart.

Temperature

NASA/JPL MUR daily analysis, displayed on its native 0.01° grid.

1 KM / 0.6 MI · DAILY

Water color

Sentinel-3 OLCI at about 4 km where available. Cloud gaps use the daily gap-filled analysis. The pass date stays on screen and the header names the source.

~4 KM · DAILY

Currents

Arrows show surface-current direction and speed.

0.2° · DAILY

Eddies

Blended altimetry identifies candidates nightly; B.I.L.L. draws the estimated half-amplitude radius.

8–120 NM ESTIMATED RADIUS

Bottom

Optional GEBCO context for the ledge, drop, and canyon walls.

GLOBAL

Wind, tides, moon

Wind folds into the projection. Tides name the gauge and its distance. Moon needs no signal.

MOON WORKS OFFLINE

Engineering

How the chart is prepared.

Two knots of set, fifteen of wind, one answer
Current 2.0 kt Result · set 041° Leeway · 3% of wind DEFLECTED RIGHT IN THE NORTHERN HEMISPHERE

South of the equator the same wind deflects the edge left.

  • Displayed on the source grid.MUR temperature uses its native 0.01° analysis cells. Tap-to-read selects the nearest displayed source or analysis grid cell, with no app-side interpolation.
  • Projected forward.When current data is available, the break can be projected to the arrival hour. A matching wind forecast can be included.
  • Hemisphere-aware leeway.The current default applies 3% of wind speed at 15°, right in the Northern Hemisphere and left in the Southern Hemisphere.
  • Eddy candidates updated nightly.Estimated half-amplitude radius comes from blended sea-height data. Rim, break, and current can provide corroborating context.
  • Reduced offline mode.Previously loaded SST, water color, and sargassum grids can be restored from the on-device cache. Live updates and new areas need a connection.

Public data sources.

NASAMUR sea temperature
ESA CopernicusSentinel-3 ocean color
NOAASea height, wind, tides, fill
MET NorwayGlobal wind
GEBCOBathymetry

Straight Answers

  • Clouds BlockCloud can block infrared for days. Water-color gaps use daily gap-filled analysis; pass dates and sources stay visible. Projection uncertainty widens.
  • Not a chartplotter.This is a planning tool. It doesn't replace a GPS or official charts. Verify against them, every time.
  • Works from published feeds.The ocean layers are not real-time; source ages vary. Changing ocean layers show source or analysis time where applicable.

Pricing

Free chart & plans available.

Pricing may vary when App Store availability opens.

B.I.L.L.

Free

No subscription required

Look at your water before you decide anything.

  • SST chart and tap readout
  • Explore available water before upgrading
  • No account, no email, no trackers

B.I.L.L. Pro · Monthly

$34.99

/ month

Billed monthly

On for the season, off when you're not going.

  • Projection up to 48 hours
  • Available Pro tools across supported regions
  • Cancel any time in your Apple Account

B.I.L.L. Pro · Annual

Best value

$99.99

/ year

Equivalent to about $8.33 a month

About the price of three monthly periods.

  • Everything in Pro, billed once
  • Use supported regions across seasons
  • One annual billing period

B.I.L.L. Pro pricing is monthly or annual. Final App Store price, availability, billing period, and terms will be shown before purchase. When available, subscriptions will be managed through your Apple Account. Terms · Privacy

Built for offshore planning.

Free SST and tap-to-read. Pro adds projection up to 48 hours in supported regions.

B.I.L.L.

Breaks. Isotherms. Layers. Location.