I was surprised to read in an answer to one of the Last Word's previous questions that sea snakes don't live in the Atlantic Ocean.

While snorkelling on the north coast of Cuba last September, both my partner and I repeatedly saw what I can only describe as a sea snake - it was thin, about 1 metre long with dark and pale markings. It was swimming among thin sea grass about 3 metres down.

The locals didn't seem at all surprised that we'd seen one, and told us with much mirth that it was poisonous.

What did we see? Was it just a land snake that fancied a swim?

Darren Darby, London, UK

(The photograph shows a yellow-bellied sea snake, and was taken in an aquarium (Image: David Burgess/Wikimedia Commons))

In Australia, the loud, shrill call of "Cooee!" is often used over long distances in rural and mountainous areas to draw attention to oneself. What is it about this word that makes it more audible over distance and is there a word more suited to drawing attention to myself should I be lost in the outback?

Tom Langford, Brisbane, Queensland, Australia

(Image: stock.xchng, sciucaness)

Plenty of speculation on this one so we're keeping the file open for a while. Thanks to those who point out that "Gooweet" was devised by Australian Aborigines for gaining long-distance attention, while a few hundred years back "hoooooha" was popular in Sri Lanka - Ed

My husband is in his fifties, weighs 105 kilograms, smokes, drinks and never, ever, takes any exercise. Yet his body is perfectly firm, no sagging whatsoever, very much like a freshly caught mackerel. The rest of us need incessant trips to the gym to avoid looking like jellyfish.

Can his incredible luck be explained in biological terms? And given that a nice firm body is an obvious advantage in the breeding game, why isn't it more widespread?

Ingebjørg Storeide, Stavanger, Norway

In a clumsy effort to seduce her, I was trying to explain the evolutionary advantages of sexual reproduction to a female friend the other day, one of which I said was introducing an element of genetic competition into the process. She wanted to know why, if two sexes are needed to create genetic competition, why aren't there three, four or a million sexes to create even more competition? So why are there only two?

Tim Rowland, Bristol, UK