Solinda Waterbabies are one third of the weight of full-size watermelons and can be carried in the palm of the hand.
They contain no pips, have almost no white inner skin, and are said to be less watery with sweeter flesh.
They have won a national listing again in Morrisons until September, with the addition this time of The Co-operative Group and Somerfield.
Solinda Waterbabies are designed to appeal to single households or smaller families for whom a full-size watermelon has been too large and has led to wastage. Other selling points are the fact that they take up less space in the fridge, are easier to carry in a shopping bag or picnic basket and are easier to slice.
The Waterbabies variety was developed by Syngenta Seeds and is grown in Italy and Spain.