In most applications, underwater acoustic transmissions have to be ada
pted to the environmental conditions (vertical, horizontal or slant li
nk, multipaths, noise...). The Multimodulation Acoustic Transmission S
ystem is a new concept which acts as a modern whose modulation schemes
and baud rates are remotely controlled by the operator. Three types o
f modulation are implemented in the same system: Phase Shift Keying (P
SK) for vertical transmission, Chirp and Frequency Hopping modulations
for horizontal communication. The user can select in real time the tw
o main parameters (modulation and baud rate), test the reliability of
the transmission and finally decide to use the modulation scheme and t
he baud rate which will insure the best quality. The underwater unit i
s then remotely programmed by the acoustic link. The system is describ
ed in detail with emphasis on the types of modulation; results obtaine
d during campaigns at sea are presented.