San Diego, California - Without a fence to mark the international boundary, crossing by boat from San Diego into Mexico might seem deceptively easy. But San Diego sport fishermen and others drawn to the waters off Baja California should take heed: Mexico's federal government has been stepping up inspections, checking for passports, tourist permits, fishing permits and other documents.

Until now, violators have been issued warnings and told to turn around. But this week, the Mexican government announced its intention to crack down on violators. That could mean boats being towed to Ensenada for an administrative process and immediate deportation of the crew and passengers.

Although violators won't face charges, "it will be an inconvenience," said María de los Remedios Gómez Arnau, head of the Mexican Consulate in San Diego.

The warning is being issued through Mexican consulates across California, and as far as western Canada and Arizona, and states that the "Mexican Navy and immigration authorities are strengthening their presence in Mexican waters."

According to Mexico's federal government, 40,000 to 50,000 tourist vessels cross into Mexico each year, many for fishing but others for other activities such as racing or cruising.

Although fishing permits long have been required, the federal government has more recently been asking foreign visitors to comply with Mexican immigration regulations, requiring them to carry passports and tourist permits when inside the country's territorial waters, within 12 miles of the coastline. Known as an FMM, the visitor permit costs about $21 USD.

In recent years, the requirements have been cause for confusion. "I think the core of the issue in many cases is that people are willing to follow the rules; they're just not sure what they are," said Ken Franke, president of the Sportfishing Assn. of California, which represents 170 marine recreational businesses.

Mexico has been working with members of the San Diego boating community to clarify the rules. In March, the country's federal government launched a website and app that include links and instructions in English and Spanish for obtaining fishing and visitors permits.

Sharon Cloward, president of the San Diego Port Tenants Assn., said she worries that some may not yet have received word of Mexico's plans to pursue immigration violators. "The bottom line is that nobody's ever enforced it, so this is all so new; that's my biggest concern," she said. "We want to make sure we're getting the information out to everybody."

Franke offered praise for the consulate's efforts: "The Mexican government is really doing outreach to the American public to make them feel comfortable to visit their country," he said. "You need enforcement to make sure everybody is in compliance. That's no different from the CHP monitoring speed on the freeway."