Yes. It's called an OTEC (Ocean thermal energy converter) and it's a very old idea.
They are quite workable. In the simplest form, you have a 2 vacuum chambers at the surface, and a pipe to the bottom of the ocean. You vacuum out your pressure vessel down to around 3psi and let some warm surface water in one end, while pumping cold bottom water into a radiator in the other. At 3psi, the surface water flashes to steam in vessel A, drives a turbine into vessel B, and then condenses back into liquid water on the radiator. This brings the system pressure back down to where you started.
In practice, you'd probably use the surface water to warm a working fluid that is a gas at surface temperature and pressure, and then the system can stay at atmospheric pressure.
The benefit of this system is that it also creates an artificial upwelling of nutrients from the bottom of the ocean, which can be used to grow all sorts of stuff. Was a big hippy fad idea back in the 70's.
In practice, you'd probably use the surface water to warm a working fluid that is a gas at surface temperature and pressure, and then the system can stay at atmospheric pressure.
The benefit of this system is that it also creates an artificial upwelling of nutrients from the bottom of the ocean, which can be used to grow all sorts of stuff. Was a big hippy fad idea back in the 70's.