Margaret River on a rainy day When it rains down south, head underground

Starting a rainy-day plan on a jetty sounds backwards, but the best of this one is below the waterline. At the far end, the Underwater Observatory takes you 8 metres below sea level down a spiral staircase, to a viewing chamber where the fish are the ones out in the weather.

The jetty runs 1.841 km into Geographe Bay, the longest timber-piled jetty in the Southern Hemisphere, and the solar train does the return trip in about 45 minutes. Tours depend on the weather, wind and sea, so check on the morning.

Origins Market on West Street is a permanent indoor market, with produce, artisan goods, food and drink all under one roof.

For some local history, the Busselton Museum is in the Old Butter Factory on Peel Terrace, run by volunteers from the Busselton Historical Society. Check hours before you go.

Margaret River Roasting Co roasts in Vasse, and its cafe sits inside the working roastery. Order a coffee and watch the next batch roast while you drink this one. It's a good way to wait out a squall.

At Carbunup River, Discover Deadly keeps more than 40 species of reptiles, amphibians, arachnids and birds in indoor and outdoor enclosures. Keepers give talks and run feeding sessions through the day. Some of the residents have eight legs, which is either the draw or the warning, depending on who's in the back seat. Check hours before you go.

Ngilgi Cave near Yallingup goes 36 metres underground, and you explore it at your own pace, with a guide in the main chamber to answer questions. Allow about an hour and a half for the whole visit. Inside there's an optional crawl tunnel for kids who'd rather do it the hard way, and a nature play area at the end.

This stretch is gallery country, too. Christian Fletcher Gallery in Dunsborough shows landscape photography. Around Yallingup there's the family-owned Yallingup Aboriginal Art, and Yallingup Galleries, with paintings, sculpture, ceramics, glass, jewellery and furniture.

Inland at Metricup, Gabriel Chocolate makes bean-to-bar chocolate at its own factory on Harman's Mill Road, and the cafe attached does hot chocolate. On a day like this, that's less a treat than a public service.

In Cowaramup, Seven Seas Tea blends loose-leaf by hand in small batches, at the same address as its shop. Temper Temper is where two chocolatiers, Roz and Georgia, hand-temper their bars, and Mukau Giftware & Gallery has an upstairs gallery in the middle of town.

On the main street, the Margaret River Fudge Factory has a window onto its kitchen, where you can watch fudge being mixed, poured and cut. The family has made it by hand here since 1999. Plan on staying longer than you meant to.

Vasse Virgin has a store on the main street, with olive oil soap, skincare and a pantry range built on its own extra virgin olive oil. Near town, Olio Bello has a tasting room on the olive farm it has harvested since 1998.

South of town, Caves Road lives up to its name. Mammoth Cave is self-guided, with an audio guide. It holds fossils of long-extinct megafauna, among them a 50,000-year-old zygomaturus jawbone still set in the cave wall. Lake Cave is a guided tour. You enter through a sinkhole and go down to a permanent lake, with a crystal formation called the suspended table.

Calgardup is 300 metres long, with boardwalks and handrails, and suits all ages. Giants Cave is the other end of the scale: ladders, rock scrambles and tight squeezes, down to 86 metres. Save it for whoever still has energy to burn at stop seven. Jewel Cave, near Augusta, is the largest show cave in Western Australia, on a guided tour of about an hour.