Almost all pond pumps are designed to be submersible, some submersibles are also equipped to be used "in line" or as external pond pumps. The popularity of submersible pumps is due to the fact that they consume lower amounts of power and are very quiet as they sit in the water. They can be fit into the skimmer box or in a pump vault of a pondless water feature. Submersible pumps allow for an almost unlimited number of installation options making them an ideal choice for first-time pond owners or experienced koi pond aficionados. Submersible pond pumps should be cleaned regularly especially in dirty water to ensure a long life of impeller and intake systems. If freezing is ever a concern it's best to remove the pump as freezing can damage some of the models unless specified in the manufacturers specifications.