As far as beaches go in Croatia it's pretty much perfect, plus it's actually warm! The Adriatic is usually pretty chilly up until the later summer months, but Šunj is shallow enough to suck up all the sun's heat from early spring.
It also means you can stroll out through the ocean for about 200 meters before it gets you-gotta-swim deep. Which gives everyone plenty of room to play rackety- smackety a.k.a beach tennis.
Get there early-ish. It's about a 20 minute walk from the waterfront or you can get a golf buggy for £8 (70 kuna).
If you decide to walk, follow the golf buggy track, don't turn right along the walker's footpath. It'll cut about 5 minutes from your journey but it's all down slippery steps & smells of soggy leaves.
Rent a sun bed for the day (about a fiver) & smell the BBQs waft into shore from the yachts & small boats that settle in the bay for the day.
I bet you've always wondered where the tallest palm trees were in south east Europe. Well, there you go ladies & gents, Lopud Island.
Lets hope it's your million dollar question.