We headed to Tumbledown Bay today, ostensibly to try out the new snorkelling gear Santa brought us for Christmas. The water was murky and absolutely freezing, so it wasn’t exactly the best snorkelling, but it was a great day at the beach, regardless.

The seals were probably the best part of the day. There were lots of them, and they were vocal and active most of the day. A couple of them were even body surfing. They’d catch a wave and leap along with it almost all the way to the shore, then swim out and do it again. It was great fun to watch

The rock pools were great, too, as they always are. We saw some starfish, lots of snails, limpets, and chitons. I never get tired of them. In the sandier pools there were lots of marine isopods (sea slaters). I sat for a while at one pool and watched them. Some were just 3-5 mm long and the colour of sand. Some of the sandy-coloured ones had a white diamond on their backs. One, almost 10 mm long, was rusty orange with a white diamond on its back. The most spectacular was about 8 mm long, and had red and yellow markings, reminding me, oddly, of a European goldfinch.

As I sat there, I realised I had no idea whether I was looking at one species of slater with many colour variations, or twenty species.

A little research at home revealed that I’m not alone in my lack of knowledge of New Zealand’s marine isopod fauna. There are just 211 aquatic isopod species described for New Zealand. Scientists estimate that there are about eight times that many species. It’s not just the deep-water types that are poorly known, but many of the easily seen intertidal species are also undescribed. It seems these common little scavengers have been largely overlooked by science.

So the mystery remains—how many different isopods did I see today? As far as I know, no one can tell me the answer. But rather than disappointing me, the knowledge that we just don’t know excites me.

Anyone who thinks we know everything about planet Earth and the only real frontiers are in space is sorely mistaken. There is so much to be discovered, not just in exotic locations like the Amazon rainforest, but on the beaches that thousands of people visit every year, in the rivers and streams we cross daily on our way to work, even in our own back yards. There is so much about which we understand so little. The scientist in me quivers with excitement.

Did I see one species of isopod or twenty? No one knows. Doesn’t it make you want to go to the beach and peer into tide pools to find out?