Watermelon and cantaloupe are transplanted often. Advantages of transplanting include earlier harvest, better control of plant population, and less seed cost per acre since seed germinate under better conditions.
Cucumbers are normally direct seeded, since there are so many more plants to the acre.
All of these crops have very brittle transplants and need to be handled very carefully when being planted. They should be planted when the plants have three true leaves. Larger transplants tend to become intertwined and break during handling. Recommendations on this web site do not endorse any commercial products or trade names.