They are submersible, sorry I try to tell most people but failed to do so with yours. Eheim bought Jager but could not keep the UL listing and had to do with reapplying and getting recertified for UL listing.
This was the reply from Eheim that another RC user got when asking them
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JAGER heaters are fully submersible according to European standards.
However since the production of JAGER heaters was moved to Germany when
EHEIM acquired the company, a new UL certificate must be issued for the
"New" company. This new certificate must be issued to comply with the
North American standards, until then the heater must be labeled as not
submersible in North America. Please note that all JAGER heaters comply
with ETL standards, which is the European Equivalent of the UL
certificate.