The data can be parsed by two regex steps.

The first tags the lines.

The second converts each line into a [t:]tide-level element.

Here is part of those two steps:

<p:regex select="h:pre" pattern=".+" matches="line"/>
        
<p:regex select="line" pattern="^(\S+)\s+(\S+)\s+(\S+)\s+(\S+)">
  <p:template>
    <xsl:param name="group-1"/>
    <xsl:param name="group-2"/>
    <xsl:param name="group-3"/>
    <xsl:param name="group-4"/>
    <xsl:variable name="month" select="substring-before($group-1,'/')"/>
    <xsl:variable name="day" select="substring-before(substring-after($group-1,'/'),'/')"/>
    <xsl:variable name="year" select="substring-after(substring-after($group-1,'/'),'/')"/>
          
    <t:tide-level date="{$year}-{$month}-{$day}" level="{$group-4}">
      <xsl:choose>
        <xsl:when test="$group-3='EST'">
          <xsl:attribute name="time"><xsl:value-of select="$group-2"/>-5:00</xsl:attribute>
        </xsl:when>
      <xsl:when test="$group-3='EDT'">
        <xsl:attribute name="time"><xsl:value-of select="$group-2"/>-4:00</xsl:attribute>
      </xsl:when>
       ...
    </t:tide-level>
  </p:template>
</p:regex>