The first sub, 4473 Sub - U1, aka the Blue Planet, carries a crew of 2 in comfort and style.
I'm glad to see a female crew member, and I put her in the pilot seat. The rear crew member handles communication with the surface, monitoring the sub's battery power and so forth. The Pilot steers the U1, and works the grabbers and lights. Note the thumb lever on the grabbers which make them easier to open.
Once the crew have boarded, the compartment is sealed with a watertight seal, held in place by the top fin.
There is limited upwards vision through a round roof window, and due to the design of the light brackets they cannot point upwards. This could be fixed with an extra floodlight mounted in the spare hole visible in front of the round window. I think this is intended to let air bubbles out, but an extra mounting shouldn't prevent this. Alternatively one of the lights could be mounted on the top, rather than underneath, the rail.
With an attachable motor, weights, hose & pump for diving, this is the Rolls-Royce of the submarine fleet.
Water tests proved the crew compartment 100% watertight, even after several hours immersion. The vessel did sit slightly nose up while diving, but not badly. Once on the bottom of course it was on an even keel again.
For play, I found the U1 is a bit big for a bathtub, but would work well in a paddling pool or ideally a private swimming pool like Richard's. I wouldn't recommend it for seaside play, as the arms and lights might be knocked off and lost.
Next comes the 4478 SUB-U2, a one man bubble shaped submarine, which I've nicknamed the Subble.
The Subble has fixed lights mounted on the roofbar, twin propellers for drive & steerage, but only one very short arm with no grabber for manipulating things. This could easily be added using spare parts, and a second arm mounted on the left if desired.
The roofbar is cleverly designed to lock the Subble closed, and there was very little leakage into the crew chamber after several hours immersion.
The Subble is self-sinking with its weights, so no need for a pump and hose. I found it worked very nicely dangled on the lifeline & hook, and by twisting the line in my fingers the Subble could be steered round the bathtub.
4478 Subble & 4479 Deep Diver 03 for size comparison.
Here's the 3611 Nautila, a sub I got last year, and unusually manufactured in Spain. Much smaller windows, and one grabber arm and one floodlight arm. These arms could be mounted on the Subble as the fittings are the same. My Nautila did leak slightly into the cabin despite an apparently watertight seal, but again nothing major.
The Nautila comes with a motor, weights, pump & hose, but I haven't shown the pump and hose here.
Nautila, Diver & Subble for size comparison. All three are in the same yellow plastic, so they form a nice set.
Now the orange of the U1 looks an odd choice. The long white arms make manipulating objects slightly hard because there aren't enough joints, but they could be replaced with the Nautila arms, with extra links added to extend the length.
Overall each set has its good points, and though I haven't yet compared them with real world counterparts, thay all look the part and seem like they would work, and have threir place in a real-world fleet for observation and other diving uses.