Growing in Float Trays

The ones in the link are special tobacco float trays. if you google tobacco float tray and look at the pictures you will see how they are different to the trays we use over here .They are more like root trainers that float like a boat in a bath of water.
The ones over here sink as they are unable to take the weight of the soil and plant. I grew most of my salad and herbs just floating them on my fish pond. I never found any slugs or snails with scuba kit on