The renewable firms all have their sights on the Pentland Firth, which is considered one of the best locations in the world for generating electricity from the power of the tides.
Yesterday, the Crown Estate, which owns the seabed and will authorise any offshore green-energy project, announced it had invited 38 companies to submit detailed plans for schemes in the Pentland Firth.
This is the first stretch of water off the UK to be opened up for development of marine renewables, meaning successful companies will be building among the first marine green-energy projects in the world.
Each company hopes to install dozens, or even hundreds of green-energy devices, such as tidal turbines, in the ocean.
Alex Salmond, the First Minister, hopes it will help Scotland become a world leader in green energy.
He said: "The fact that so many companies have already registered their interest in developing wave and tidal energy projects in the Pentland Firth and surrounding waters is extremely encouraging.
"The Scottish Government has recently launched the world's greatest-ever single prize for innovation in marine energy, the 10 million Saltire Prize, and the opening of the Pentland Firth for development is a timely and crucial move."
The Crown Estate invited initial expressions of interest in the Pentland Firth from renewables firms in November. A spokeswoman said she could not reveal how many companies had shown an interest because of competition rules, but she confirmed 38 firms would be invited to the next stage – to tender for sites in the Pentland Firth.
They must now submit detailed applications, spelling out how many devices they want to install in the water, by the end of May.
The Crown Estate will decide which are suitable, and the companies will then have to apply for planning permission from the Scottish Government.
Calum Duncan, Scottish conservation manager for the Marine Conservation Society, welcomed renewable technologies, but said the possible impact of the devices on sensitive seabed habitats must be considered, including the likely affect on mussel beds and feeding areas for fish, basking sharks and seabirds.
Liam McArthur, the Liberal Democrat energy spokesperson and MSP for Orkney, also welcomed the strong interest but had reservations. "This energetic stretch of water will be a challenging resource to tame," he said.
"We still know relatively little about the Pentland Firth and what will happen when we start putting devices in the water there.
"While the Pentland Firth is often described as the Saudi Arabia of tidal power, the challenges it presents also make it the Mount Everest."