Please advise whether you are allowed to go paddle boating during the Sefira. Thank you!
Yes, this is permitted.
The customs of mourning in the Sefira period are limited to not having weddings, music and dancing, and haircuts and shaving.
See Tzitz Eliezer Vol. 11:78, Shu”t DIvrei Malkiel Vol. 3:5, Orchos Rabeinu Vol. 2 pg. 95.