The Coastguard has urged people to heed government advice and stay at home after three people on a yacht had to call for help.
The 33ft vessel got stuck on a shingle bank at Selsey Bill at about 17:30 BST on Sunday, HM Coastguard said.
It managed to free itself and an RNLI lifeboat escorted it into deep water.
The Coastguard warned: "Every 999 call could put frontline responders at risk of Covid-19 and places avoidable pressure on our vital NHS services."
It said the government had been clear that during the pandemic people had to stay at home to save lives.
"We've had incidents at the coast and on the sea, including yachts aground and pleasure boats broken down. This shouldn't be happening," it said.
The RNLI said its Selsey lifeboat crew arrived just after 17:50 BST to find the yacht had floated off the bank.
It said the crew, who were on a journey to Hartlepool from Falmouth, reported "everything was OK and they were happy to carry on" with their journey.
It escorted the yacht out to safe waters before returning to its station.
The RNLI said it was surprised to get a call to a yacht aground after the advice from the government, but said crews would always respond to an emergency.
Members of the public have responded angrily to the posts.
Gavin Pryde said: "Leave them to it. The instructions were clear. Don't put yourselves at risk because, hopefully, we may need you in the future."
Albany Motor Yacht Club said it was "outrageous behaviour " and a "blatant disregard for the safety of others".