It's one of the great pleasures of cruising to explore the element below you. Dan Bower considers the practicalities of going underwater

When cruising in the tropics – or indeed sailing round the world – the time spent actually sailing is surprisingly insignificant and, apart from the ongoing task of yacht maintenance, provisioning and just existing, the rest of your time is spent exploring and adventuring.

On Skyelark Dan and his wife like to get to see the islands and get a feel for life on shore, so harbour time is usually spent hiking into the mountains, cycling the coast paths or taking tours, hiring cars and frequenting restaurants, yacht clubs and bars. But the one thing they do nearly every day at anchor is head off for a snorkel.

To dive or snorkel

On many of the reefs and passes the snorkelling is as good as the diving and has the advantage that it requires little planning or equipment and is the kind of activity you can do on whim for an hour whenever you choose. Diving, however, shouldn’t be discounted as the depth does give you access to bigger and more plentiful fish and mammals, and opens up possibilities and sites further offshore. The South Pacific, in particular, is considered to host many of the best dive spots in the world.

Dont miss

Reef dives – Reefs are plentiful around many of the islands, and are usually accessible to both snorkellers and divers at different depths. Expect to see varying levels and types of coral, small tropical reef fish and occasional bigger reef predators such as barracuda, grouper and snappers. If you’re lucky, you might also see sharks or rays.

Passes – Some islands have narrow gaps in the reefs, which can make for excellent snorkelling, particularly in the Pacific atolls. When there are only a small number of passes, the incoming tidal currents can create fantastic drifts.

A drift dive is where you start up-current and just drift along, playing the astronaut. In some of these passes you can easily be travelling at three or four knots, which doesn’t sound much, but the sensation of flying through the ocean seeing wonderful reefs and fishes on the way is amazing!

Typically, you also see bigger fish, sharks and perhaps dolphins playing in the pass as you’re on the boundary between ocean and lagoon. You should always dive the passes at slack water or on an incoming current, so that you end up in the safety of the lagoon, and the water quality is that much clearer. The outgoing currents can be very strong and can create standing waves so a bit of planning is required.

Do’s and don’ts

Do have fish identifiction charts on board.
Do go as often as you can.
Do buddy up if going far fom the boat.
Do always snorkel passes on an incoming tide.

Don’t touch or take anything from the reef
Don’t fin up lots of sand/sediment
Don’t feed the fish