Croucher, who has more than 20 years’ experience in travel, joined Not Just Travel in January 2020 having previously worked at Tui, P&O Cruises, Cunard, Regent Seven Seas and JTA.
The move comes after the firm reported "surging" cruise sales as a result of its continued investment into the market.
Cruise bookings are predicted to rise from 12% of all NJT holiday sales from pre-September periods, to 25% of all holiday sales during peaks.
Croucher said: "It’s an exciting time for both the industry and consultants. Training will be engaging and inspiring. This is the beginning of a fun and exciting journey for trade partners, consultants and their customers."
NJT co-founder Paul Harrison added: "Duncan’s previous history of creating fantastic sales results for the likes of Tui and P&O, followed by the last two years helping travel consultants significantly increase their sales makes him uniquely perfect for this role."