I’ve been lucky enough to twice visit the Spanish island of Mallorca this year to engage in my passion for snorkelling.

The Mediterranean is such a diverse place for marine life and on almost every dive I come back having seen something new.

One feature this year has been the sheer abundance of jellyfish – most notably mauve stingers and compass jellyfish. But there were also comb jellies and ‘by-the-wind sailors’, the most unusual creature I think I have ever seen.

These jellyfish were especially numerous in the spring, but were still pretty prolific on my most recent visit in October.

In previous years when snorkelling in the Mediterranean I have only occasionally seen jellyfish – so what is going on?

It is an issue that is causing a bit of debate among marine scientists, with climate change, ocean acidification and pollution, and overfishing of predator species all being cited as possible reasons.

The mauve stinger (pictured) in particular is a most beautiful species, but let me tell you this; the sting is pretty nasty as I found to my cost in the spring. The Mediterranean is highly dependent on tourism, so it would be highly undesirable economically if this jellyfish abundance were to continue in future years.

Perhaps there is some unexplained natural phenomena going on – nature does tend to have boom and bust tendencies – and numbers will fall back in the future. But whatever the case, both scientists and tourism bosses will be monitoring the situation closely.