Is there a nautical equivalent for "battlefield"?

Is there a specific term to describe the area of a sea on which a nautical battle (perhaps between two large fleets) takes place?

Somehow the term "battlefield" seems inappropriate when there is no field.

Solution 1:

Historians and tacticians of Naval Warfare, depending on the point in history, will have different interpretations of what actually constitutes the area of engagement.

In battles such as at Thermopylae (480 BCE), ships needed to engage each other with grapples, and board to take by hand-to-hand combat (unless they were ramming). With the introduction of firepower, naval battles like Trafalgar (1805), or even Jutland (1917) depended on the range of the guns, which was no more than 400 metres (18 pounder) in 1805 and a maximum of 32 miles (and incidentally out of sight) in 1918.
The next most important development was the introduction of naval air, as seen most effectively used in the attack at Pearl Harbor (Dec. 7, 1941) and launched from a distance of some 400 kilometers.
More recently, Guided Missle Frigates (FFG) (all decommissioned since 2015) and Destroyers (DDG), armed with Tomohawk Cruise Missiles, are able to attack from a distance of 30 to 50 miles.

Aircraft carriers of the Nimitz class can effectively launch an attack from a range of 2000 Km, while SSBNs can strike with nuclear capability from a distance of up to 11,000 km.

So an exact word defining the area of naval engagement may be difficult to come up with.

However, all that being said, ngrams turns up many usages of

Naval Battlefield

which is 2 words.

Extending the range of surface- launched naval projectiles to miles — as opposed to yards — the surface- to-surface missile has transformed the naval battlefield. No longer do warships have to be in sight of one another to engage in combat.

-The Cape Route: imperiled Western lifeline (1981) Robert Hanks

To define the Naval battlefield with sufficient spatial and temporal resolution to support 21st century warfare will require hybrid systems which combine remotely sensed environmental information fed to weapon systems...

-Satellite oceanography: hearing before the Subcommittee on Oceanography and the Great Lakes of the Committee on Merchant Marine and Fisheries, House of Representatives, One Hundred First Congress, first session ... April 27, 1989

[emphasis added]