Renwick came through the Chapel Gate ranks before continuing his progress at Hartpury - playing for their successful midweek University side on Wednesdays - as well as 'doubling up' with Bristol side Clifton in National Two South on Saturdays.
After narrowly falling short in their promotion play-off last season against Guernsey, Croker says Renwick is just the sort of player his squad needs to keep everyone on their toes.
Croker said: "Hamish is another wonderful acquisition for us having been away at university studying at Hartpury College in Gloucestershire, and playing for their midweek team and then playing for Clifton on the weekends in National Two South.

"He is a really, really talented boy - he is very good over the ball in terms of turnovers and has a really high skill set and is a really good communicator.
"He is versatile enough to play anywhere across the backrow, so it is going to be an exciting season seeing where he links up with everybody."
Croker says he has not "100 per cent" decided where the best position will be for Renwick to play yet.
But with no pre-season match this weekend following the narrow 31-26 loss to former Championship fliers Birmingham and Solihull at home last Saturday, Croker can have a good look at Renwick.
Croker added: "He has played all of his age group rugby coming through at Bournemouth and went onto play south west rugby and many felt he was unlucky not to push on from that and go a bit further.
"We are delighted to have him back - he is a proper Bournemouth boy - he really loves the club and he is prepared to go that extra mile for his team-mates and I'm really looking forward to seeing which position we play him in."