On 16 June 1940, Morse, under the command of Jean Georges Charles Paris, struck a mine and sank in the same minefield off the Kerkennah Islands that sank her sister ship Narval six months later.

The submarines' electrical propulsion allowed it to attain speeds of 9 knots (17 km/h; 10 mph) while submerged and 15 knots (28 km/h; 17 mph) on the surface.

Their surfaced range was 7,700 nautical miles (14,300 km) at 9 knots (17 km/h), and 4,000 nautical miles (7,400 km) at 12 knots (22 km/h), with a submerged range of 70 nautical miles (130 km) at 5 knots (9.3 km/h).

At the outbreak of World War II, she served in the Mediterranean Sea and was part of the 4th Submarine Flotilla in Bizerte.

Morse blew up on a mine in the same minefield off the Kerkennah Islands that sank her sister ship Narval six months later.