I hate to be the “party pooper,” but I must also go on record and remind you that having sexual intercourse in public places, such as the beach, a public swimming pool, a swimming hole or lake, etc., is illegal.
Finally, although the idea sounds romantic and sensual, underwater sex is not the smartest choice. For starters, sexually transmitted infections and HIV can still be spread while having sex in the water; this is even true of hot tubs. This means that it is important to use birth control during water sex that can provide STD protection
Latex condoms are effective at preventing pregnancy and STDs but may be somewhat risky to use during underwater sex, regardless of whether or not you are in a chlorinated pool, cold or warm water, or the ocean. If you plan to use this form of contraception, be aware of some important information about condoms and water sex. This includes the lack of research, condom interactions with chemicals and heat, lubrication, and additional complications like putting the condom on and the possibility of it slipping off.