ITS LESS WELL-KNOWN to non-locals, but when the weather and tides are against you in Cornwall there are always dives in Falmouth Estuary, or a little further along the coast in the Helford River.
These are not the first places that come to mind when you think of diving in Cornwall, but they are under-rated.
Even confirmed wreck-divers have been known to come up after a dive in the estuary or river, excited about the number of scallops collected for the barbecue, or the number of thornback rays they have seen.
Diving in some parts of Falmouth harbour and estuary is not allowed, but enter the water near the Eastern Narrows buoy, on the Carrick Roads section of the estuary, and you will not be disappointed.
Whether its bits of spidge, something for tea, or photography, this area has it all. However, as shipping has increased here lately, do check movements with the pilots before diving.
Dropping about 10m, you are met by a carpet of pink maerl. The maerl beds in the Falmouth estuary are the biggest in England and stretch for acres, spreading east towards the shore.
Maerl is a coralline algae, and always reminds me of the metal jacks children used to play with, though each knobbly piece is unique.
Look closely as you fin over the maerl and you will see that it teems with life. Dozens of brown and creamy-coloured tube anemones push their way through the carpet, waving delicate tentacles to catch anything nutritious that might be passing.
The beautiful, aptly named eyelash worm will often disappear once it detects any movement near its tentacles.
Tiny gobies dart here and there, their translucency making them hard to spot if stationary. Dozens of hermit crabs, laden down by either a cloak or parasitic anemone living on top of their shells, crawl about, trying to find the easiest routes to negotiate.
Heading slightly deeper, huge spider-crabs may suddenly rear up triffid-like from concealment in mounds of weeds, their backs thick with sponges and bits of algae used for camouflage.
Thornback rays lie still and wait, only at the last moment taking off to find a resting place away from the bubbling creatures who invade their space.
You may often find the sandy patches away from the maerl covered in scallops. Be aware that moves are afoot to ban scalloping in particular areas along the Cornish coast.

FOR THOSE WHO LIKE COLLECTING bits of tat, bottles and pieces of crockery litter the seabed, thrown overboard from the big ships that used this thoroughfare on their way to Falmouth. Years ago the sea was a common dumping-ground, and the odd treasure can be found.
Two bottles I retrieved on one occasion were nothing out of the ordinary, but some divers have been more fortunate, and brought up some very old champagne bottles.
As the bottom starts to slope to 20m, you reach the edge of the old river that once ran through the valley here. An almost vertical drop to around 30m will then bring you to the bottom. This is sometimes a better place to start, depending on what you want to do, but bear in mind that no deco-diving is allowed in the estuary, and you must surface on the east bank.
Further south along the coast lies the Helford River, and in many respects it affords similar diving in terms of marine life, though no maerl beds.
High salinity means that, unlike at many dive sites in Cornwall, kelp is evident in quantity only when it gets washed into the river after a storm.

DROPPING INTO LESS THAN 10M of water on the northern side of the river, the first thing I see is a large thornback ray resting on the sandy bottom among the bright green eel-grass that grows everywhere.
Frantically trying to get my camera organised, I grab a couple of shots before he moves off. Every time he pauses, I try to manoeuvre towards his front, but hes having none of it. Eventually I give up, and he glides off into the gloom.
Turning to the eel-grass, I notice numerous snakelock anemones clinging to the slim leaves, their waving tentacles placed to catch passing food.
Checking out the fine shingle covering the sea-bed I can see tiny gobies everywhere, darting across the bottom away from the huge eye of my camera.
Scallops snap shut, suddenly aware of my approach, or shoot off performing their mad, jerky dance in the water column before coming to rest.
Shoals of tiny two-spot gobies dart about, keeping together like a well-trained dance troupe but parting before me as I swim over the eel-grass.
There are many hermit crabs, completely camouflaged by the anemones on their backs, living in perfect harmony with each other. Unlike in the estuary, however, I see only parasitic rather than cloak anemones.
I watch one particular crab with an anemone like a fluffy top hat about three times his own size on his back; as he moves it lurches from one side to the other, causing him to stagger about like a drunk after a night out.
While my booty from the dive is just a few photos, others have had different treasures in mind, and bags of scallops are emptied out to sort through.
A couple of edible crabs also make an appearance before being banished to separate bags, so its a successful end to a very under-rated dive.