It seems dating in the sea is just as complex as on land, with male dolphins off the West Australian coast observed offering up presents to females and cultivating "wing man" relationships to help each other score a mate.

Researchers have examined coastal dolphins off the State's north coast and found something rarely seen in mammals — males gifting females large sea sponges ripped from the ocean floor.

They've also been seen tossing them about, possibly to show affection and strength.

Simon Allen, from the University of Western Australia's School of Biological Sciences, said the humpback dolphins' gifting activities could be similar to human dating behaviour.

"It could be gift-giving in the sense that humans do it — diamond rings [and] roses and the like — in order to impress a female or to suggest that he is somebody that would be a really wise idea to mate with," he said.

"It appears the females tend to be ignoring the male and then it kind of ramps up to the point where he's a bit frustrated and he tosses the sponge in the direction of the female."

A humpback dolphin pushes a sponge in an attempt to impress a potential mate. ( Supplied: UWA (Josh Smith) )

Dr Allen said the male dolphins also sing in an attempt to win the females over.

"Prior to or after a sponge presentation we have also heard a trumpeting sound coming out of the blowhole, which was completely unexpected," he said.

"I guess if you're trying anything to impress a lady then that's the way to go."

The research also found that the male animals appeared to develop a "wing man" in other male dolphins.

"Just like sponge presentation or gift-giving, this is very rare among non-human mammals. We also form complex alliances," Dr Allen said.

"It would make some sense to work with a partner."

Male dolphins also call on their acrobatic abilities to make an impression. ( Supplied: UWA (Simon Allen) )

Romance, threat or showing off?

The behaviour was initially discovered by accident before it was studied in detail.

Dr Allen conceded the singing and gifts could be a display of threat rather than romance, similar to courting chimpanzees who try to coerce females into mating.

But the behaviour could also be a display of strength designed to impress the females.

"We know that the sponges are firmly fixed to the sea floor," he said.

"They have to withstand things like 10-metre tides in the Kimberley … so it would require some strength to take the sponge from the sea floor, and of course they don't have opposable thumbs or even hands."

Dr Allen and other researchers spent 10 years examining the behaviour. Next, they hope to demonstrate whether the efforts of the male are actually successful by examining behavioural observations and genetics.

"We would really like to get some more data and work out whether or not these adult males who engage in these multi-modal sexual displays are fathering more offspring — the key test to whether this is a great strategy."