Basements. Yards. Construction sites.
What do these things have in common? They all can flood.
But with the help of a dewatering pump you can restore all these places to their proper dry state.
When shopping for a dewatering pump there are a few things you'll need to consider.
Inlet Size

Dewatering pumps have an inlet size ranging in size from 1" - 4". No matter the size, they all work the same way. It sucks in water through an inlet valve and ejects it from a discharge valve.
Essentially the difference in size just means the bigger pumps can get the job done more quickly. If you need to empty a pool, any size pump will get the job done. A 4" dewatering pump will finish a job 4 times faster than a 1" pump.
Low-Oil Shutoff

All gas-powered engines need lubrication to run properly. This is done with engine oil, which also prevents the engine from overheating. If you run an engine without oil you can ruin it.
With that being said, look for a dewatering pump with a low-oil shutoff feature. This will automatically stop the engine from running when it's low on oil, preventing further damage.
Roll-Cage

Depending on the setting in which you'll be using your dewatering pump, you may want to consider a protective roll cage for the pump. This helps to protect the pump in case it should fall or have something dropped on it.
Another feature to look for is anti-vibration dampening. These are essentially just rubber mounts between the pump and the protective cage, keeping it in place and so it doesn't rattle and make more noise than necessary while in use.