It is, but rather difficult and expensive for short to medium distances. Submarine power cables are often HVDC.
The Sylmar grounding system is a line of 24 silicon-iron alloy electrodes submerged in the Pacific Ocean at Will Rogers State Beach[4] suspended in concrete enclosures about one meter above the ocean floor.
The grounding system at Celilo consists of 1,067 cast iron anodes buried in a two-foot trench of petroleum coke, which behaves as an electrode, arranged in a ring of 2.02 mi (3,250.87 m) circumference at Rice Flats (near Rice, Oregon), which is 6.6 mi (10.6 km) SSE of Celilo.
And even more interesting is they are replacing/replaced it! https://www.circlingthenews.com/terminus-of-sylmar-ground-re...
- HVDC uses voltages between 100 kV and 1,500 kV.
- HVDC can be cheaper for 500+ mile runs
- HVDC allows power transmission between unsynchronized AC transmission systems
- Recent advances make UHVDC feasible (800kV+)