are you under EASA/FAA/Other? generally this is a grey area, at least in EASA world. I think the key is in the SEP (Sea) rating description - To act as PIC during water operations of a SEP seaplane. There is absolutely nothing about this on EASA web site, it's as if the rating doesn't exist. I interpret this as - if you are sticking with dry ground landings /take offs you are absolutely fine.
However, whenever in doubt contact your local authority.