After three years being at the Belgian Military Corps of Cadets in Lier, he joined the Royal Military Academy Brussels (110TA) September 1970.
On September 26, 1972, he became lieutenant.
After different functions on board of different types of MCM navy ships, he became Commanding Officer of the MSI M474 TURNHOUT.
1979 – 1980 : Patent of Officer specialized in artillery and missiles.
1980 – 1983 : Artillery Officer on board of F911 WESTDIEP and F912 WANDELAAR
1983 – 1984 : Artillery Officer and Head of the Operational Department on board F911 WESTDIEP
1984 – 1987 : Belgian Naval Staff, Deputy Missiles and artillery in the undersection Plans and Programs/Weaponsystems (ZDP/W)
1987 – 1988 : Commanding Offcicer of the MCM vessels M918 DIANTHUS and M917 CROCUS (Octopus/Calendar Two).
1988 – 1990 : COMINAV, Schoolcommander of the Belgian School for the instruction of Officers.
1989 : Corvet Captain
December 1989 : Executive Commander of F910 WIELINGEN.
Corvet Captain Seymortier is married and has two children.