We do not recommend immersion in the ocean at this time. It raises a number of halachic and safety concerns, sticky sand being only one of the factors.
We are in close contact with health professionals who have assured us that using a mikveh that adheres to health guidelines is safe at this time. The treatment of the water kills the virus.
Do prepare at home, even taking a shower right before arriving at the mikveh so that you can just inspect yourself visually and immerse straight away, to minimize your time there. You can even bring your own towel as a further precaution.
We commend you for your commitment to Torah and mitzvot at a challenging time. Wishing you good health and besorot tovot!