I am floating on the surface of an unsettled sea, in the neighbourhood of the Silver Banks off the Bahamas. It is mid-February, and the water is warm, though I wear a thin wetsuit which wards off the sunshine as much as the slow chill of the sea. Around me are scattered, like leaves on a pond, some other humans from the mothership. We are all doing our best not to let our excitement get the better of us. "Make like jellyfish, people!", our guide had told us, and we try - oh, how we try! But as we travel sideways through the regular chop-and-splash of the wavelets, our eyes are wide with wonder. For below us, increasingly visible as the gentle breeze and slight currents waft us over them, are humpback whales, the grandes señores de la mar, the great lords of the deep. (Females come here every year to give birth in these warm, shallow waters. Mother and calf spend a few weeks here resting and preparing for longer migrations to faraway feeding grounds. Rogue males are here too, however, signaling their presence with deep groaning songs that make the rubber hulls of our little RIBs vibrate; we can simultaneously feel their power through our feet and hear their drawn-out longing. They are broadcasting their interest to the females as well as warding off unwanted attentions from other, unwelcome suitors. And they are hard to find, playing a very deliberate game of hide-and-seek). The first thing our straining eyes see of mother and baby is the pale gleam of pectoral fins. As we slide nearer, the brilliant whiteness of these fins against the milky blueness of the waters makes our eyes ache. Mamma and Baby doze in an inverted position, heads down, tails upright in the 20 metres' depth. But Mamma can hold her breath longer than Baby and so, after perhaps 10 or 15 minutes, the little one - all five metres of him - comes slowly to the surface. And if we are lucky enough, he will indulge his natural curiosity by coming over to check us out. Which is why, of course, I have a deathlike grip on my old Nikonos V with its 20mm lens and viewfinder, and why too my fingers have gone numb as they wait to see if Baby will come play with us. And come to us he does, and passes slowly around our group, eyeballing us as we gaze back through masks and lenses. And everyone is delighted, until he swims behind us and puts us between Mamma and him. It's an awesome experience to watch an adult humpback whale arise from the depths towards you. Its dark flesh covered in barnacles, it reminded me of nothing so much as watching one of our major motorways coming up to meet us. It seems to happen so slowly, and yet she's suddenly there, right beneath me, now beside us, and then leaving us all in her wake, the calf tucked protectively under one flank... It's only then that I realize that I'm out of film, having preset the rangefinder dial to 3 feet to infinity and altered aperture to maintain at least a 1/60th second shutter speed. I don't remember having taken more than half a dozen shots!

Once we're certain Mamma and Baby have finally left us, the surface erupts with whoops and shouts and clenched fists punching the air.

And it's still only midway through the first morning of a whole week's whale-watching. Is this not the easiest and most enjoyable way to take memorable underwater photographs?

I think it might be!