Jonathan Leslie and Jennifer Lewis, who are all set to get married this Friday, were forced to make a last-minute venue change after watching fire crews battle the blaze at The Baths on Sunday night.

The Sydney couple had already been staying in Sorrento ahead of their pending nuptials and were shocked to see their venue gutted by fire.

Mr Leslie praised the quick work of the The Baths' owners who managed to sort out a new venue for 80 guests at short notice.

"It's the sort of story you hear about happening to other people but not to you," Mr Leslie said.

Investigators have found the cause of the blaze was an electrical fault in a storage area next to the kitchen.

Devastated brides-to-be posted on social media on Monday, desperate to find alternative venues for their special days.

High school sweethearts Jai Smith and Meaghan Woolard were due to marry at The Baths on Saturday. They had just returned from a wedding rehearsal when Ms Woolard's father delivered the bad news.

"She just basically fell to the ground and started crying," Mr Smith said.

"We have five days now to organise a whole new wedding. All the personal touches that we were putting on it at The Baths, it's all gone."

Radio station Fox FM has offered the couple their South Melbourne studio rooftop for the wedding, but this creates transport dilemmas for the couple, whose 100 guests have already booked accommodation in Sorrento.

• Did you have a wedding booked at The Baths? Email us scoop@theage.com.au

The devastated owner of the Mornington Peninsula restaurant said he was relieved no one was injured in the fire.

CFA crews were called to the restaurant about 8.15pm Sunday.

The desperate efforts of at least 11 fire crews failed to save the Port Nepean Road restaurant, which overlooks Port Phillip Bay.

Owner and manager James Gibson said on Facebook on Monday that the restaurant was thankfully closed at the time of the fire.

We are devastated that The Baths restaurant has burnt down. Thankfully no customers or staff have been injured, as it...Posted by The Baths on Sunday, October 18, 2015

Customers with weddings booked are urged to contact the venue for assistance with alternative arrangements.

"We are devastated that The Baths restaurant has burnt down," he said.

"Thankfully no customers or staff have been injured, as it was a Sunday evening and the restaurant was closed."

On Instagram, Mr Gibson posted an illustrated quote: "There is always something to be thankful for."

"It is still too raw for us to post any pictures of tonight's fire, however I found this picture and thought it was quite fitting," he wrote.

The Baths is about 1.5 hours' drive from Melbourne.

It was named after the Sorrento Sea Baths, which were located on the same site in the late 1800s and early 1900s.

The CFA's Arthur Haynes said it took an hour to control the fire, with specialist crews called from Frankston and Mount Martha.

Point Nepean Road remains closed.

With Benjamin Millar, Rania Spooner