Dreamlines, which is backed by Rocket Internet, Global Founders Capital, Holtzbrinck Ventures, Target Global, Dimaventures, Hasso Plattner Ventures, and TruVenturo is working with GCA Altium on the deal, which could value it at more than 200 million euros (176.7 million pounds), the people said.
The loss-making company, which has a target to break even this year with earnings before interest, tax, depreciation and amortisation of 4 million euros on revenues of 60 million, has asked for indicative bids in the 40 million fundraising by Thursday.
Separately, smaller but profitable peer e-hoi - backed by former Porsche head Wendelin Wiedeking as well as his partners Michael Sautter and Klaus Droste - is also considering raising capital from investors, the people said.
The cruise industry is expecting global passenger volume to increase to 30 million this year, having grown by half over the last decade, according to industry association statistics.
At the same time, demand for traditional package holidays is waning and Thomas Cook, one of the industry's largest suppliers, folded earlier this week.
The companies were not immediately available for comment, while GCA Altium declined to comment.
(Reporting by Arno Schuetze, editing by Kirsten Donovan)