Submarine Robo joined the Machine Robo Series in 1983, as one of the new figures issued by Bandai, largely based on real-world vehicles. The following year, Tonka added the toy to the Gobots range, renaming it as Dive-Dive, and around this time the figure was added to the European Robo Machine line.

The character appeared occasionally in the Challenge of the Gobots tie-in cartoon (notably getting key roles in "Cold Spell" and "Depth Charge", and was generally one of the more likeable characters. A few bootlegs appeared throughout the decade, notably a grey version in the Convertible Robots line.

The toy was among those chosen for the 1993 Robo Machines reissue line, with copyright complications (Hasbro own all the Gobots names and so forth; Bandai own the moulds) seeing the figure issued as simply Submarine - this version also has the 'US Navy' decals modified to read 'RM Navy'.

A submarine is another example of a charming, different Gobot alternate mode. Based on a Los Angleles class nuclear submarine (assuming the 723 pennant number is correct, it's the USS Oklahoma Bay), it's a rather large submarine, and thus there isn't a massive amount of detail on the thing (though the cartoon portrayed him largely as a midget sub, something that proved Hanna-Barbera were contractually obligated to stuff up each character in some way or another).

Sadly, there are some rather obvious joints on the thing - the rear rudder section works loose easily due to its' secondary role as Dive-Dive's feet, while the bows also tend to do the same, being the robot arms. It's a shame that neither seems worthy of a little pin-and-hole arrangement to secure them.

This aside, the submarine is sturdy, with the conning tower parts and fins thick enough to avoid fragility. The detail level for something of this scale is nice, and the wheels on the underside are nice and subtle.

Turning a submarine (thin, cigar-shaped) into a robot without the latter being a stick on legs is a difficult art, but thankfully one Bandai have mastered here. The transformation is little fiddly in places, especially getting the arms down to his side and separating the hips, but it's worth the work as the robot is impressive.

Somehow Bandai have managed to get some width out of the robot without making him too flat either. There's also some nice detail on the chest, and the wheels for the submarine mode keep out of the way. The head cast is one of the better "chrome dome" affairs, while the big shoulders look great. The articulation is passable - the legs can't be moved without causing him to collapse, but the arms have the standard metal joints, allowing a fair bit of movement.

The robot mode looks both imposing and natural, not bad considering how slim the alt mode is. The hips do look a little awkward, but this is really only a minor problem.