Rescuers are continuing to try and save a stranded humpback whale off Germany's north coast.

The marine mammal, which is stuck on a sandbank, was first spotted in Lübeck Bay on Monday.

Diggers have been deployed to dredge a channel back into deeper waters.

Characterised as a race against time, the rescue mission's attracting huge interest.

It's even being livestreamed from Timmendorfer Strand, a seaside town in Schleswig-Holstein.

Estimated at being 12 to 15 metres long and 15 tons in weight, it's thought the whale could have previously become entangled in a fishing net.

Rope is said to still be stuck in its mouth.

Experts believe it's a young male that may have accidentally wandered into shallow waters.

According to NDR, others have speculated that it's possible he was seeking a final resting place.

But the exact reasons leading up to the whale being stranded aren't known.

There are warnings that the chances of saving him are very slim but rescuers aren't giving up.

"For the whale, this is obviously a stressful situation," said Stephanie Gross from the Institute for Terrestrial and Aquatic Wildlife Research.

"He's been here in the shallow water for three days now and isn't feeding at all at the moment," although she added the animals can go without food for weeks.

German media reports that conditions are tough at the sea-shore with an icy easterly wind.

Another challenge is the fact that this is such a heavy creature and one in a weakened state. Divers have been in the water to get a closer look.

Marine biologist, Robert Marc Lehmann, told NDR he found the whale's skin "looks terrible" but he is responsive.

"It's reacting, it has both eyes open, it's vocalizing, but it's incredibly uncertain and it's scared," he said.

Other efforts to get the whale moving – using high tide, rotating it or creating large waves with boats – have so far failed, according to NDR.

"I hope the channel is deep enough that material will slide down and that this will motivate the whale to swim in. And if not, then he'll have to be given a little nudge," Robert Marc Lehmann told the broadcaster.