On a busy weekend there can be as many as 10-20 other divers, but turn up mid-week and youre likely to have the lake all to yourself.
Along the side of the car park closest to the water are a row of breeze-block platforms, each topped with kit-friendly wood. Reverse your car up to one and you can unload, assemble and don your gear as easily as you can imagine.
Such facilities ought to be mandatory at any inland dive site with pretensions to adequacy.

THE SLOPE IMMEDIATELY behind the platforms offers a gently shelving entry that someone with a kind heart might even call a beach (and is, by the way, an ideal place for landing casualties, if your day out isnt complete without a mock medical emergency).
However, most divers use the purpose-built stage at the end of a tongue of land that extends out into the lake proper. A set of steps allow divers into waist-deep water, perfect for photographers with cameras, or you can make a stride entry from the outer edge of the platform, if you can cope with dropping into just 1.5m of water.
Beneath the surface, youll find a rope leading straight to a platform thats ideal for any drills you might feel need a little work. Once youre bored with fettling, youll see more ropes leading away from the platform to take divers straight to the different sunken attractions.
Go left and youll find a little cabin-cruiser, a set of big concrete pipes and eventually a larger fishing boat.
Go straight on and the line starts to branch, but you can find more platforms, cars, a van, a caravan and, if you follow the correct piece of string far enough, a small yacht.
Go right from the first platform and you find another platform, and a sunken car a bit further on, if youre willing to risk a swim without a line to follow.
The lake also supports a healthy stock of fish, with some big perch, a good number of large pike and a fair few European eels, plus an incredible diversity of invertebrate and larval creatures. Take a look at some of these little horrors through a decent macro lens; youll have nightmares for weeks.
The pike are a challenge to photograph. Theyll hang around and allow you close enough to get a picture, but at the same time stay far enough away to ensure that its one of those low-contrast, colourless, hazy and really disappointing shots that end up in the bin. How they do this I have no idea, but they can judge the distance beautifully.
The eels are far more accommodating. They let you get really close, either supremely confident in their camouflage or too dumb to realise that youre there. Then they suddenly jet off to another part of the lake at very high speed.
Usually, but not always, they move away from you, but sometimes they rear up and fly past your mask, which is always fun when youre diving with someone who has never seen eels before.
Which brings us to the downsides. Some people swear that theyve had 11m depth, but I have never managed more than nine, which is a statistically significant difference, even by the standards of the average political party.
On the other hand, this does mean that the lack of an air-station isnt much of an issue. You should get two decent dives from a single cylinder, unless youre a real air monster.
It also means that narcosis isnt going to blunt the experience, though the vis might. Youll normally get 3-5m, and it was nearer 10m last year, but it can be as little as a foot after heavy rain.
Not that it matters much. Even if you lose the lines and didnt take a bearing, the lake isnt so big that you can get into much trouble, even though I despise surface-swimming.
Entry is currently £5 per diver, and youll find the lake on the road between Scorton and Northallerton, not far from Catterick and the A1. If youre there on a summer Saturday or Sunday morning, theres even a butty wagon!

Ellerton Park Lake, Scorton, Richmond, North Yorks. 01748 811 373, www.ellertonpark.com