open TELEMAC-MASCARET The mathematically superior suite of solvers

Dear colleagues,
Has someone already managed to mask elements located at mid-depth with T3D (to simulate an immersed body) ?
I tried to use the following code in MASK3D but the model crashes at the beginning of the simulation :

IF(NETAGE.GE.2) THEN
DO IETAGE = 32,36 !!! There is 66 planes in my model
DO IELEM2 = 1,NELEM2
! MASKEL(IELEM2,IETAGE) = MASKEL(IELEM2,1)
I1=IKLE2(IELEM2,1)
I2=IKLE2(IELEM2,2)
I3=IKLE2(IELEM2,3)
IF((INPOLY(X(I1),Y(I1),XSOM2,YSOM2,4)).AND.
& (INPOLY(X(I2),Y(I2),XSOM2,YSOM2,4)).AND.
& (INPOLY(X(I3),Y(I3),XSOM2,YSOM2,4)))THEN
MASKEL(IELEM2,IETAGE) = 0.D0
! print*, IELEM2,I1,I2,I3
ENDIF
ENDDO
ENDDO
ENDIF

Any suggestion would be highly appreciated.
Thank you.
Cheers,
Jérôme