Answer: There can be few reasons why surface on water can be harmful to the bacterial colony.
Step-by-step explanation:
It is possible that while preparing the media for the bacterial colony that the constituents might not have been taken right proportion and water is more in it.
It tends to float on the surface and if the bacterial colony is not able to grow in such an environment it will led to the death of the colony.
There are chances that the mobility of the bacterial species increases in water and because of this there will be problems faced at the time of isolation.