This picture has nothing to do with this post but who could resist imitation
liquid cheese (next to the yoghurts in my local supermarket)?

Rough seas, important lessons, feuding dogs

For the last couple of days, the sea here has been rough, which makes diving there difficult. The reef is only about four metres deep and, when there are waves on the surface, the water underneath churns back and forth, throwing you all over the place, kicking up the sand and making visibility poor. This means that, for Tullio my instructor, we have the perfect conditions to go for a dive and learn some new skills. ("If you can do it in this," is his mantra, "you can do it in anything.")

First up, I have had to learn 24 little underwater mimes that are used to teach people diving skills – such as how to clear water out of your mask, how to adjust the air in your inflatable jacket to make yourself perfectly buoyant, how to relocate your air supply when your buddy kicks it of your mouth, and so on. Underwater, obviously, you can't use words, so each lesson is a series of slow gestures that you show them and that they then repeat. It's harder than it sounds and kind of absurd, especially when it is something like take-all-your-equipment-off-in-a-special-sequence-hold-it-in-front-of-you-and-put-it-on-again-while breathing-normally, a skill whose purpose, to be honest, I have never really understood.

I also, today, led my first dive, with Tullio pretending to be a customer. This was a strange and not altogether successful experience. As soon as we set off, I realised I had never been at the front of a dive before. I usually pootle along behind someone, taking in the fish and stuff and letting them worry about where we are going. Now, the whole of the sea was in front of me and I had to navigate us around, looking for interesting marine life, and making sure we didn't end up in Cuba. If you are familiar with a dive site, this isn't so bad, there are landmarks and things, but this afternoon felt like the underwater equivalent of getting lost on Dartmoor. Every corally/planty thing looked the same. Bits of rock seemed to come round again and again, and most of the time, with the visibility so poor, I thought I had lost my "customer". We did manage to end up back at the beach after 30 minutes but Tullio's opinion was that if he had paid for this dive he might want his money back.

To be serious, it was, obviously, a good learning experience. Presented with a new situation, I forgot almost everything I knew, swam too fast, breathed too much air, bounced up and down (rather than gliding elegantly from one place to the next) and came out exhausted. Oh, and my tank nearly fell off. But, of course, that's the point. We came back safe, if a bit dissatisfied, and next time will be better. And I learnt, again, the golden rule of scuba (and, really, of anything): if you find yourself getting worked up by something difficult, stop, take a few breaths, ground yourself again and carry on.

Tomorrow is my day off and I think I will go up the coast to Playa del Carmen. I need to buy two things to make my home life a bit more comfortable: one of those Italian metal coffee pots, which seem to be non-existent in Tulum, and some little speakers to play music out of my laptop. On the big bus between here and Cancun (Playa del Carmen is halfway) they show DVD movies, dubbed into Spanish and played at ear-splitting volume. When I came here from the airport, the bill was Beverly Hills Chihuahua 2. Having somehow missed out on Beverly Hills Chihuahua 1, and with my Spanish pretty rusty, it took me a while to get the hang of what was going on. Worse, we arrived at Tulum just as the final scene (some sort of dog-talent-show stand-off between a snooty poodle and our working-class chihuahua hero) was coming to its climax. I imagine chihuahua power triumphs in the end but maybe this time I'll find out for sure.