first /setblock ~ ~ ~ spawner

then get a cod/salmon/guardian/elder gaurdian spawn egg and put it inside the spawner to test if it is working.

these water-living-creatures can only be spawned under water so please put spawner inside water.

get squid spawn egg(I was testing squid & glowsquid when I discovered this glitch), put it inside the spawner.

wait for some moments, until the little mob inside the spawner are spinning at high speed. 

It can't generate it at all!!

then put the water-living-mobs egg inside it again, they spawned at once.

P.S. the glow squid does not affected at all. Actually, it can even generate on land. that is maybe another bug.