Chazal decreed not to swim lest you come to make a floatation device. However, this does not apply to a pool with a rim that keeps water from flowing out. (ShA 1 – see MB 326:21 that the custom is not to bathe at all lest you come to wring out your hair)
It is ossur to splash water 4 amos distance out of a pool in r’shus horabbim. (MB 4)
You aren't allowed to clap, slap your thigh, nor dance on Shabbos. It is a fence so that you do not come to fix a musical instrument. This prohibition includes tapping and snapping your fingers. Using a rattle to calm a baby is also ossur. (ShA 3)
On Simchas Torah you are allowed to dance and clap (only) to honor the Torah. (MB 8)
Backhanded clapping is always mutar. (ShA 3)
The Rama justifies a minhag to be lenient to clap, slap your thigh and dance. However, you should not be lenient if not for a mitzva. Do not protest against those who are lenient. (Rama 3 – MB 10)
You are allowed on Shabbos to incarcerate a man who wants to leave his wife as an agunah. (MB 14)
Other than the above, no one should be disturbed from his menucha on the holy Shabbos. HaKadosh Baruch Hu wants that the wicked should not be punished on Shabbos. (MB 13)
If a person neglected to light Shabbos candles before shkia, she should not light them during bain hashmashos,. (MB 19)
It is best to avoid making a wedding on Erev Shabbos. (MB 19)
You are allowed to pledge tzedaka on Shabbos. (MB 23)
Do not do Pidyon Haben on Shabbos – it is like a business deal. Pidyon Haben must be after 30 complete days have passed. It is not enough to wait 29 days, 12 hours and 793 chalokim (a lunar month) from birth. Therefore if the 31st day falls out on Shabbos, it gets postponed until after Shabbos. (ShA 4 – MB 27)
Completing a marriage involves a monetary acquisition which is forbidden on Shabbos and Yom Tov. The husband now has a potential to inherit his wife and to own her salary/handiwork. The wedding canopy completes the marriage for a besula. However, for a widow or divorcee, the marriage is only completed with beeah rishona or at least a yichud haroi beach. If, for some reason, the husband did not perform a yichud haroi beach before Shabbos (e.g. the kalla was a nidda until Shabbos), he may not do the beeah rishona on Shabbos. (ShA 5 – MB 32)
You may not enter a boat or ferry on Shabbos. This is included in the decree against swimming. If the boat bottom is sitting on the bed of the river you are allowed to board. Likewise, if the boat is tied to the dock you are allowed to board. See above Siman 248 that if you made the boat your house before Shabbos you aren't bound by this gezaira. (ShA 7 – MB 35,36)