Whoa! not familiar with the TJM but I can't see it being too different to my old Safari which has been on for almost 20 years. On mine the way the head sits causes water to be pushed to the back and sides of the head, water then runs down the edge of the snorkel body, what gets into the filter flows slowly and drops out through the drain hole in the filter base.
Very interested to hear feedback from other TJM users.
Live in Darwin and haven't had a problem at all, are you sure it came in via the top and not a incorrectly sealed air box.
We also use a K&S re useable filter, more about helping with dust ingestion, but at least it can also handle water.