Book Cover: Water Hazard
Part of the Cardinal Oaks series:

On the way to becoming more than friends, Zahra and Rose's relationship faces its first obstacle--Zahra's ex, Sorcha, has resurfaced and is in need of a soft landing. When she shows up earlier than expected and starts giving off mixed signals, Zahra's forced to confront her own feelings for Sorcha. When it appears that her career as a marine biologist is leaving her landlocked, Zahra has to make a choice. Help her ex find her wings, or keep tying her down by comparing her to the past.