Different OTCs will do different sports and adventure training activities at a different times, depending on who is in the unit and who wants to organise things.
Most OTCs will have various forms of skiing trips on offer.
Depending on the OTCs budget - all of which (as with the rest of the TA) have been cut this financial year, you may or may not get paid for it. In many cases what you do is that in theory you get paid but the money from your pay is used to subsidise the trip, and so it ends up really cheap.
Your profile name suggests you are from Pompey. In which case your nearest OTC is Southampton- which recruits from Portsmouth Uni as well as those in Southampton. Southampton run a really active programme of offshore sailing. They won the Army sailing championships this year and are entering a team in the Fastnet race.
Be aware the ethos in the OTC is subtly changing. The budget has been cut this year (forcing units to concentrate on those who are committed) , and there is a lot more emphasis in most units on profesional military training and training people who are reasonably serious about looking at a career in the armed forces, rather than the old ethos of a military university club.
It is still very much good fun and there are some fantastic opportunities. For example the SUOTC Fastnet team will be doing the worlds most challenging yact race for free in a fifteen berth yacht from the Services Sailing Centre. To enter the race as a civvy expect to pay several thousand punds.
For a good idea of the sort of things that go on in OTCs, have a search on various units web sites. They all do roughly the same sort of stuff.
All OTCs recruit once a year only at the start of the Autumn term , so make sure you check when their recruiting events are being held and get along.
have fun