I don't think so. I think people blanch (cook very lightly) the vegetables so they sink. You could attach the cucumber to a weight so it sinks too. If you cook vegetables, they lose their vitamins.
actually that's not true- lightly blanching (or briefly boiling) vegetables allows critters like fish and birds to digest and absorb vitamins more efficiently. Also, I woudl go with zucchini instead of cukes- more nutritious.
