AndyRoo said..
Flat water to start then move to small perth metro waves.
115 kg isn't super heavy, there are plenty of boards out there that will carry you...but be aware that board behaviour and dynamics are different once you're much above 100kg. 70-80kg shop guys even with the best intentions don't speak from experience of it, you MUST demo and find out for yourself.
For a first board at your size, flat water cruising to first small waves START looking around 11-12 ft, 200 litres, 32-33" wide as a benchmark but do try a few either side of this, it's not just about volume and width...shape, rails and rocker will all have a bearing on a board's handling. When you get right into things, fins also make a difference, especially for heavyweights.
A few suggestions below - they will get you into first waves but still have decent glide and won't be slugs in flat water:
Fanatic Allround 11' or 11'6
Starboard Atlas or Big Easy
Surftech Laird 11'6 or 12'
Even the Naish 12' might be worth a look.
If you have more ambitions towards surf, look at:
9'10 Allwave
10' Naish Mana (hoping to try the new one today)
10'2 NSP
10'6 Fanatic Allround
10' Coreban EZ
Just to name a few, there are plenty of others around those parameters.
Demo demo demo. Just to illustrate the horses for courses thing , at 6'2 and in the mid-high 120s here's my quiver:
Starboard Atlas (my first board and a keeper) - small waves and flat water cruising, even the occasional race
9'10 Allwave (surf up to about shoulder height)
12'6 x 30" Red Air inflatable
Walk on Water 14 x 29" (298L) for downwinding
Naish Glide 17' x 26.75" 320L for distance
And
14 x 29" NSP/DC 293L for training/racing
Go forth and demo, don't be in a hurry. Feel free to PM, happy to share a few thoughts from the big end of town.