Hi 9A
Whilst I don't want to comment on whether it is sensible to carry lifejackets and do HUET training etc. and I don't know anything about Italian air law - under EASA, it is only a requirement to carry lifejackets and floats (multi-engine CAT) when flying more than 10 minutes from land, so technically if the sea route is less than about 40nm you can fly without. If I remember correctly, the EASA AMC is pretty vague about HUET training too.
TeeS