A flow measuring system detects fluid flow in a subsea well. A disclosed flow measuring system may comprise a housing 12 attached over a hole 22 or riser aperture, defined within a riser 20, creating a fluid pathway. Continuous louvers 27 may span the riser aperture, filtering the flow of fluid reaching the fluid pathway. The direction and volume of flow within the fluid pathway may be measured by sensors attached to the housing. In an alternative embodiment, director plates 29 may be integrated with or integral to the louvers with the director plates influencing the flow of fluid to, within and out of the fluid pathway. The use of flow measurement sensors within the fluid pathway is also disclosed. In one embodiment, no louvers or director plates are used, thus increasing the fluid communication between the riser and housing.