The fantastic Playart submarines were definitely one of my favourite toys of my child hood. The submarine on the right is the earlier version powered by the same slide on motor that powers the Playart Torpedo boats amongst other Playart boats , and incidentally many other boats from other manufacturers of
this era.

These submarines dived and surfaced repeatedly . You could adjust the depth they dived to , and also make them cruise on the surface. The submarine on the left is the 'improved' version powered by two Penlite (HP7 , AA) batteries , as opposed to the single Penlite of the earlier version, held vertically under the torpedo behind the conning tower. I and a friend had endless fun with these when we were kids. Superb toys.

Because , as all submarines , whether real, model or toy , they are sensitive to buoyancy, modern batteries being a bit heavier and bulkier than the old 70s Penlite HP7 batteries, it's sometimes tricky to get these submarines to dive correctly.