TIDEPOOL
What the tide leaves behind
A rocky shore at low tide is one of the richest little worlds you can walk into, and most of us crouch over a rockpool with no idea what we're looking at. Tidepool is a friendly pocket guide to the crabs, shells, sea stars, anemones, snails, urchins, seaweeds and darting little fish that live where the land meets the sea.
- CRABS
- SHELLS
- SEAWEEDS
- SEA STARS
- ANEMONES
- URCHINS
Every creature gets a recognition note in plain language: what to look for, where it hides, the colours and sizes to expect, and how common it is. Enough to put a name to the thing clinging to the rock in front of you.
Life on the shore sorts itself by the tide, so the guide is built that way too: a drawn shore-zone cross-section places each creature in the splash, high, mid or low zone where it really lives.
The finds log
Mark each creature you spot, add the date and a note about where you were, and watch a progress ring fill as you work through the guide. A day at the beach turns into a collection.
The identify quiz
Name a creature, place it in its tide zone, or sort it into its group. Each answer comes with a short explanation, and your best score is kept.
Browse by group, by zone or by colour, search by name, and open any species for the full picture, including a note on which animals to admire and leave in place rather than handle. A short etiquette page covers the rest: watch the incoming tide, mind slippery rocks, and put everything back as you found it. Pick an accent colour, turn the gentle water motion on or off, and take it anywhere along the coast. Fully offline, no account, no ads.
Get Tidepool on Google PlayPackage com.shorewise.tidepool
On Australian shores in particular: some of the prettiest things in a rockpool can hurt you badly, among them blue-ringed octopus, cone shells, stonefish and blue-bottles. Tidepool is a guide for looking, not a safety check and not a foraging guide. Don't pick anything up to identify it, don't eat anything you've identified with an app, and keep an eye on the water coming back in.
The water doesn't come back in evenly
Between low and high water there are roughly six hours and twelve minutes. People picture the sea creeping up at a steady pace, but it barely moves in the first hour, races in the middle two, then eases off again. Sailors call the shorthand the rule of twelfths. The real shape is closer to a cosine curve.
| Hour | Rule of twelfths | Cosine curve |
|---|
With a two-metre range, the fastest moment is halfway through, at about 0.84 cm a minute, or half a metre an hour. That's the moment when a pool you're standing beside fills back up in the time it takes to photograph a crab. In the first hour the same tide moves only about 13 cm.
The two methods agree exactly at the second, third and fourth hours. They part company at the ends, where the rule says an eighth of the range in hour one and the curve says a fifteenth. And the whole thing repeats about 50 minutes later each day, because the tide follows the moon, not the sun: successive high waters come around 12 hours 25 minutes apart.
What's not here: no creatures, no zones, no finds log. This is an idealised tide for a simple coast: real shores have double high waters, shallow-water distortion, wind and barometric pressure, and your actual range comes from a local tide table, never from this page. The shore-zone guide and the species notes are in the app.
MoonBirch Interactive
A small studio publishing Android guides from Brisbane. One subject per app, written plainly, kept offline.
- Company
- LINK ADVISORS PTY LTD, trading as MoonBirch Interactive
- Director
- Edward Foster
- Address
- 57 Berwick St, Fortitude Valley QLD 4006, Australia
Spotted something the guide gets wrong for your stretch of coast, or a species note that doesn't match what's really under the rocks there? Tell us the species and the beach. Local corrections are the most useful mail we get.